Stolen cat

Kc from Nawton

Looking for help and advice. I am looking after a family members cat while they are overseas (it's their young daughters actually). Anyway, my neighbour has in effect 'stolen' the cat, it started with it going missing for a couple of days, we went looking for it, then I saw a child who was visiting her house come out holding the cat. My husband and I went over and spoke to her about it and she all but made out that she would be keeping him. I explained to her that it belongs to my family member and said it would be going back home (out of town) on their arrival back in NZ. She basically said she would keep feeding it if she saw it which we said well no now you know its got a home (which I am sure she knew already) please don't encourage it. So then it was coming back home then all of a sudden its gone again, she keeps locking it in her house. My husband went over there tonight to talk to her again and reminded her that we are looking after it and it will be going back to its owners and she told him no that it wouldn't be it was hers now! So what can I do??