Good grief. You cannot be serious with all of this garbage. The woman needs a psychiatrist. There is nothing else for you to argue about.
The woman has a psychiatrist that says she might grow out of it. Maybe she will go into cat grooming or behaviorist. She might be a cat sitter or write books about cats. How do you know if she can be a productive person and still be a cat? She believes she has cat DNA, she has cat behavior, she has night vision.
It might be a fad of sorts or something she will live with her whole life, so what? Lycanthropy is a real syndrome that people manage to live with. Many shaman believe in animalism and being possessed by animals spirits. Tribes believe they descended from animals or birds. They manage to live productive lives.
If she want to wear cat ears on a head band, fuzzy gloves and wear of tail, who is she hurting? If she wants to walk on all fours and is afraid of dogs, what is the harm? A lot of people purr when satisfied or touched in tender ways. So what?
Maybe some her marbles are a bit out of place, but that does not mean she is missing any of them. She is not undergoing physical operations to replace her skin or bones. She is articulate enough in her language that she is making videos and giving interviews. She might turn her "cat" into a fortune and purr all the way to the bank.
Stop trying to lock her up. If she wants to tell the world she is a cat, let her.
How crazy can she really be?