Background

In this post I thought it would be interesting to explore the idea of Nymeria recognizing a "scent" on some of the Lannisters/Spicers she may encounter in the Riverlands.

If interested: The Stark/Snow Children and Warging

The Wolves Don't Like Your Scent Lannister

While this may be due to the abandoned plotline of Tyrion burning Winterfell, back in AGOT, several of the Stark direwolves (Grey Wind/Summer/Shaggy) do not like Tyrion's smell:

The door to the yard flew open. Sunlight came streaming across the hall as Rickon burst in, breathless. The direwolves were with him. The boy stopped by the door, wide-eyed, but the wolves came on. Their eyes found Lannister, or perhaps they caught his scent. Summer began to growl first. Grey Wind picked it up. They padded toward the little man, one from the right and one from the left.
“The wolves do not like your smell, Lannister,” Theon Greyjoy commented.
“Perhaps it’s time I took my leave,” Tyrion said. He took a step backward … and Shaggydog came out of the shadows behind him, snarling. Lannister recoiled, and Summer lunged at him from the other side. He reeled away, unsteady on his feet, and Grey Wind snapped at his arm, teeth ripping at his sleeve and tearing loose a scrap of cloth.
“No!” Bran shouted from the high seat as Lannister’s men reached for their steel. “Summer, here. Summer, to me!”
The direwolf heard the voice, glanced at Bran, and again at Lannister. He crept backward, away from the little man, and settled down below Bran’s dangling feet.
Robb had been holding his breath. He let it out with a sigh and called, “Grey Wind.” His direwolf moved to him, swift and silent. Now there was only Shaggydog, rumbling at the small man, his eyes burning like green fire.
“Rickon, call him,” Bran shouted to his baby brother, and Rickon remembered himself and screamed, “Home, Shaggy, home now.” The black wolf gave Lannister one final snarl and bounded off to Rickon, who hugged him tightly around the neck.
Tyrion Lannister undid his scarf, mopped at his brow, and said in a flat voice, “How interesting.”
“Are you well, my lord?” asked one of his men, his sword in hand. He glanced nervously at the direwolves as he spoke.
“My sleeve is torn and my breeches are unaccountably damp, but nothing was harmed save my dignity.”
Even Robb looked shaken. “The wolves … I don’t know why they did that …”
“No doubt they mistook me for dinner.” Lannister bowed stiffly to Bran. “I thank you for calling them off, young ser. I promise you, they would have found me quite indigestible. And now I will be leaving, truly.” -AGOT, Bran IV

If interested: Abandoned/Changed Plotline: The Siege of Winterfell

Grey Wind & Rolph Spicer

We get a somewhat similar situation after the Westerlings "join" Robb's cause with Rolph Spicer:

As they started up the steps, Catelyn asked the question that had been troubling her since she entered the hall. “Robb, where is Grey Wind?”
“In the yard, with a haunch of mutton. I told the kennelmaster to see that he was fed.”
“You always kept him with you before.”
“A hall is no place for a wolf. He gets restless, you’ve seen. Growling and snapping. I should never have taken him into battle with me. He’s killed too many men to fear them now. Jeyne’s anxious around him, and he terrifies her mother.”
And there’s the heart of it, Catelyn thought. “He is part of you, Robb. To fear him is to fear you.”
“I am not a wolf, no matter what they call me.” Robb sounded cross. “Grey Wind killed a man at the Crag, another at Ashemark, and six or seven at Oxcross. If you had seen—”
“I saw Bran’s wolf tear out a man’s throat at Winterfell,” she said sharply, “and loved him for it.”
“That’s different. The man at the Crag was a knight Jeyne had known all her life. You can’t blame her for being afraid. Grey Wind doesn’t like her uncle either. He bares his teeth every time Ser Rolph comes near him.”
A chill went through her. “Send Ser Rolph away. At once.”
“Where? Back to the Crag, so the Lannisters can mount his head on a spike? Jeyne loves him. He’s her uncle, and a fair knight besides. I need more men like Rolph Spicer, not fewer. I am not going to banish him just because my wolf doesn’t seem to like the way he smells.”
“Robb.” She stopped and held his arm. “I told you once to keep Theon Greyjoy close, and you did not listen. Listen now. Send this man away. I am not saying you must banish him. Find some task that requires a man of courage, some honorable duty, what it is matters not … but do not keep him near you.”
He frowned. “Should I have Grey Wind sniff all my knights? There might be others whose smell he mislikes.”
“Any man Grey Wind mislikes is a man I do not want close to you. These wolves are more than wolves, Robb. You must know that. I think perhaps the gods sent them to us. Your father’s gods, the old gods of the north. Five wolf pups, Robb, five for five Stark children.”
“Six,” said Robb. “There was a wolf for Jon as well. I found them, remember? I know how many there were and where they came from. I used to think the same as you, that the wolves were our guardians, our protectors, until …”
“Until?” she prompted.
Robb’s mouth tightened. “.…until they told me that Theon had murdered Bran and Rickon. Small good their wolves did them. I am no longer a boy, Mother. I’m a king, and I can protect myself.” He sighed. “I will find some duty for Ser Rolph, some pretext to send him away. Not because of his smell, but to ease your mind. You have suffered enough.” -ASOS, Catelyn II

If interested: Direwolf Kills

Nymeria & the Brave Companions/Cat's Body

While not a 1:1 comparison we see Nymeria/Arya not only hunt members of the Brave Companions:

Her dreams were red and savage. The Mummers were in them, four at least, a pale Lyseni and a dark brutal axeman from Ib, the scarred Dothraki horse lord called Iggo and a Dornishman whose name she never knew. On and on they came, riding through the rain in rusting mail and wet leather, swords and axe clanking against their saddles. They thought they were hunting her, she knew with all the strange sharp certainty of dreams, but they were wrong. She was hunting them.
She was no little girl in the dream; she was a wolf, huge and powerful, and when she emerged from beneath the trees in front of them and bared her teeth in a low rumbling growl, she could smell the rank stench of fear from horse and man alike.  -ASOS, Arya I

but also retrieve Cat's body from the Green Fork:

That night she went to sleep thinking of her mother, and wondering if she should kill the Hound in his sleep and rescue Lady Catelyn herself. When she closed her eyes she saw her mother’s face against the back of her eyelids. She’s so close I could almost smell her …
… and then she could smell her. The scent was faint beneath the other smells, beneath moss and mud and water, and the stench of rotting reeds and rotting men. She padded slowly through the soft ground to the river’s edge, lapped up a drink, then lifted her head to sniff. The sky was grey and thick with cloud, the river green and full of floating things. Dead men clogged the shallows, some still moving as the water pushed them, others washed up on the banks. Her brothers and sisters swarmed around them, tearing at the rich ripe flesh.
The crows were there too, screaming at the wolves and filling the air with feathers. Their blood was hotter, and one of her sisters had snapped at one as it took flight and caught it by the wing. It made her want a crow herself. She wanted to taste the blood, to hear the bones crunch between her teeth, to fill her belly with warm flesh instead of cold. She was hungry and the meat was all around, but she knew she could not eat.
The scent was stronger now. She pricked her ears up and listened to the grumbles of her pack, the shriek of angry crows, the whirr of wings and sound of running water. Somewhere far off she could hear horses and the calls of living men, but they were not what mattered. Only the scent mattered. She sniffed the air again. There it was, and now she saw it too, something pale and white drifting down the river, turning where it brushed against a snag. The reeds bowed down before it.
She splashed noisily through the shallows and threw herself into the deeper water, her legs churning. The current was strong but she was stronger. She swam, following her nose. The river smells were rich and wet, but those were not the smells that pulled her. She paddled after the sharp red whisper of cold blood, the sweet cloying stench of death. She chased them as she had often chased a red deer through the trees, and in the end she ran them down, and her jaw closed around a pale white arm. She shook it to make it move, but there was only death and blood in her mouth. By now she was tiring, and it was all she could do to pull the body back to shore. As she dragged it up the muddy bank, one of her little brothers came prowling, his tongue lolling from his mouth. She had to snarl to drive him off, or else he would have fed. Only then did she stop to shake the water from her fur. The white thing lay facedown in the mud, her dead flesh wrinkled and pale, cold blood trickling from her throat. Rise, she thought. Rise and eat and run with us.
The sound of horses turned her head. Men. They were coming from downwind, so she had not smelled them, but now they were almost here. Men on horses, with flapping black and yellow and pink wings and long shiny claws in hand. Some of her younger brothers bared their teeth to defend the food they’d found, but she snapped at them until they scattered. That was the way of the wild. Deer and hares and crows fled before wolves, and wolves fled from men. She abandoned the cold white prize in the mud where she had dragged it, and ran, and felt no shame. -ASOS, Arya XII

If interested: The Brave Companions/Bloody Mummers in TWoW

Nymeria in the Riverlands

While Arya is now in Braavos, Nymeria is still roaming the Riverlands at the head of Chekhov's Wolfpack:

She woke with a gasp, not knowing who she was, or where.
The smell of blood was heavy in her nostrils… or was that her nightmare, lingering? She had dreamed of wolves again, of running through some dark pine forest with a great pack at her hells, hard on the scent of prey.
...
She took a breath to quiet the howling in her heart, trying to remember more of what she’d dreamt, but most of it had gone already. There had been blood in it, though, and a full moon overhead, and a tree that watched her as she ran. -TWoW, Mercy

If interested: The Night Wolf & Arya's Wolf Dreams & TWOW

Lannister/Spicer Scent

It will be interesting to see if we get any information on Nymeria potentially coming across any of the different Lannisters (ex: Daven) or Spicer (ex: Rolph) that exude some form of "scent" that causes her to attack (or not). We know that Rolph Spicer was out in the Riverlands looking for Jaime when he was missing.

If interested: The Night Wolf & "Missing" Characters in the Riverlands

TLDR: The Stark direwolves have at times seemingly been to preemptively notice danger to their owners in some way. We see this when Tyrion arrives back to Winterfell (potential abandoned foreshadowing) as well as with Grey Wind not liking Rolph Spicer's scent. With that in mind, it will be interesting if we get to see any type of interaction between Nymeria and the Lannisters/Spicers/etc based on this "scent".