Rose, despite what some may say, is far, far from stupid. Both her father and Uncle Harry were at Hogwarts, and Victoire has been far too sad for anything good to have happened. Rose has also noticed the lack of Teddy around, and has put two-and-two together after what Albus shared with her. Teddy is gone, possibly dead, and Rose doesn't have anyone to talk to about something so tragic.
She retreats to Hagrid's. Though he's away for the time-being, he'd let any child of Ron and Hermione's into the large fenced area of the grounds where he's been collecting all sorts of creatures. Rose is sitting with an injured hippogriff, dressing his wounds while also entertaining a small group of puffskeins. She's huddled under heavy cloaks and a scarf, hardly recognizable.
It's what she does when she's scared, or sad. Animals are her life.