A cat can give love bites as a way of showing affection. It is often done while the cat is being played with or while someone is petting her. The bite is a way to show that she is enjoying the affection.
However, there are some cases where a cat may bite because she is overwhelmed by all the attention she is getting. If a cat is biting down hard rather than with a soft and gentle bite, she may be trying to indicate she is no longer enjoying herself. Sometimes, cats give a smaller bite as a warning sign before they bite hard.