Lady wants to keep my cat?

Ok, so I have this one cat. He ended up getting ringworm all over his body. Since it was really hard washing him on my own, even though I tried for a few months, after those few months, he just didn't let me wash him. He would wiggle away, climb, etc. Also at the time, I was having some domestic issues, with one of my siblings, so I found this one lady, who advertised herself as having like a shelter, and taking care of animals. She took him in for a while, I still kept the documents and everything, and I never signed away my cat. So he became better, and I at the same time found out that this lady is actually a hoarder, and neglects a lot of her animals. So I naturally wanted my cat back. So I knew since she's a hoarder, she probably won't give him up that easily, I kind of tricked her into giving my cat back, and before I could get into the car, she started screaming, circling me, going crazy basically. She even put her foot in the door, preventing me from leaving. I left, but she still harasses me every day on the phone, comes up to my house, sends people over, has people call me from different numbers, etc. I called the police, and they said how I should solve the matter with her, but they don't realize that this lady is actually harassing and stalking me at this point, and isn't well. She also sent me this message saying, I fed the cat, I got him better, so it's not fair for you to keep him. What should I do? I never told her she could permanently keep him, and it was explicit for her to help him get better....Any advice? Thanks.