It depends very much on the age of the child. Very young children often do not understand that animals have feelings, they have to be taught this.

You could try saying to her "How do you think cat feels when you do that?" See what comes back, listen to her responses and gauge her understanding. If she doesn't seem to understand then "How would you feel if someone much bigger did that to you?" I think working with her is likely to be more helpful than just telling her off.

It does depend very much on her age however, whether she is 3 or 13, there is a big difference in how you approach this.