My theory about the cat is that it is just a cat. Boring, I know. But I also think that the blonde girl has the ability to enter the mind of the cat and perhaps have it do tasks or use it as a spy. It is a lame enough power that she would never be a superhero but also allow her to get a lot of useful information if it is something she can do to all cats. Or maybe even any number of animals. I just don't see her living that pet life long term, with the cat food and the litter box and all, but being able to jump in and out of the cat's mind would be something that would be tolerable and useful. She might also have a limited ability to do it with humans, too, because she seems capable of entering MCs dreams. Or at least she was at first. Maybe he got better at shutting him out and that's why she switched to the cat.
She might still be his daughter from the future, though. She kind of resembles Harper when she takes her glasses off...