They're the only ones left from the North. Winterfell had fallen long ago due to Theon, the Boltons, the Karstarks, the…she can't even remember all of the families anymore. All of the ones that were sworn to her brother, just to come back for blood and some sort of entitlement they thought they had earned. Back then though, they all wanted to become the King of the North. Now it is all a ruin. Burned down and desolate; never rebuilt.
When she finally makes it back to her home, it's completely deserted, except for those that lie in wait for her to succumb to this sickness. The ones, that for whatever reason, have still retained their memories; but these memories are tainted because they want revenge, and all they see is her. They want revenge for this sickness that has befallen them, and she is the only real Stark left to take it out on.
She doesn't know exactly why they blame her, just that's she's there, the wrong place and at the wrong time. It started in Winterfell, months, days, years, she doesn't know, after it had burned down. The ones that stayed inevitably starved or were taken over by this need to consume human flesh. And the ones that starved were the ones that were eaten first.
They hide in the darkness, she knows. Waiting and watching. She knows they are waiting for the inevitable. The starvation or this illness that has consumed them all to devour her body and soul. She knows once this happens, once she is so weak she can hardly move, they will swarm around her and take what they so desperately want.
She finds him then; when she is the one hiding and waiting. He is the only one that does not want her dead, he remembers her as his sister. He is in the tombs with their father's bones and the bones of all before them. The place she knows he's always found the safest, even when she was small and afraid and couldn't go there on her own.
When she sees him, he's gnawing on the bones of a rat; at first she doesn't know, doesn't know whether he is just hungry and this is all that is left, or if he has become like the others too. She finds out when he sees her for the first time and doesn't recognize her at first. When he attacks her and starts clawing at her face and trying to bite the flesh that he can see through partly decomposed eyes. She screams his name as she fights him and at last he finally sees her for who she truly is.
He backs off of her and tries to say her name, but his jaw is almost gone and he cannot say the word. She is truly frightened of what her brother has become, but that love for him is not lessened. She finds hope when she discovers she is not truly alone now. Not the only Stark left. Even as he is now, he'll forever remain her little Rickon.
She does not want to be alone, and will not kill the only member of her family that is left. So she hunts for him; finds more rats in the tombs; goes out and traps squirrels and rabbits, anything that is not human she will let him eat. Far be it for her to deny him his feast.