Ownership Over A Pet

Backstory: My friend moved to CA with her boyfriend they got a cat (for her) they broke up and now he’s using the cat to get her to come back to CA. (She tried to take the cat and all her belongings with her when she left but he and his mother took her license and everything she owned and held her hostage with no way of leaving (not because she wanted to take her cat with her) ) he’s been trying to get her to call him and talk to me and my fiancé about her staying with us (the only way he said he would bring the cat to her). When that didn’t work he said he would take her to small claims court to see who gets the cat.

Her question is if he paid for this pet, but she has all the documentation that it is her cat, the signed paperwork for the cat being flown in to CA and picked up. Does she have a chance at getting her cat back or is he going to be able to keep it because he paid for the cat itself?