Well, some girls do like to date the assholes, and I've dated a long string of them in my day.

Pretty much what it comes down to are these..eh let's call them theories...

A) She liked the name calling by him, because like I said most girls like assholes. She felt as though it was his own way of flirting with her, and so she acted so disstressed about it, to egg him on more or less. And when you fought him, and won, it made him look weak. Very unattractive.

B) You attracted too much attention to her, and hurt someone she might still care about, and in most cases, that will get anyone mad at you. If you hurt someone they care about still...eh expect to be in the dog house for awhile.

C) She didn't like you getting in her buisness like that. Now, anyone can respect you for sticking up for your friend, but sometimes you have to let them deal with their own problems, otherwise you just end up in trouble with everyone.