Keeping Cats from Fighting?

I have two cats, a male and a female, both are fixed. They are 2yrs old and I adopted them at the same time. The female cat will bathe the male, but the moment he starts to to do the same to her she bites his neck and attacks him. She doesn't hurt him and he doesn't hurt her, it's just a few rabbit kicks to her head and she leaves. Why does she do this?

By Christy