How do I tell my child we need to stop feeding the neighbour's visiting cat?

My daughter had put a bowl beside the back step when the cat's owner came over and said, “Please don't feed him. We're trying to keep his diet consistent.”

I had allowed a few treats because the cat kept visiting and my daughter loved the little routine. I didn't ask the owner first. Now my daughter thinks the neighbour is stopping her from being kind: “But he comes here because he likes us.”

The owner hasn't asked us to chase the cat away. She asked us not to feed him or let him in, and said he has a diet agreed with his vet. I don't know the details, and they aren't mine to change.

[Cats Protection's guidance](https://www.cats.org.uk/help-and-advice/lost-found-and-feral-cats/found-a-cat) explains that cats can need a particular diet and that feeding a visiting cat can encourage repeat visits. That helped me realise I had treated his returning as proof that our treats were a good idea.

How do I explain the change without turning the owner into the villain? I'd like my daughter to keep enjoying seeing him, but I need to stop the bowls and the invitation through the back door.