The cat I fed died. What should I do?
There is no evidence, and there is no way. If you have evidence, you can call the Animal Protection Association to complain about her, or post on the Internet to make public opinion condemn her. I can see that you are caring, and good people will be rewarded. If there are stray animals next time, you can let someone you like take them in. After all, not everyone likes cats and dogs.