Should I Get Mad That Lesbian Is Hitting On My Girlfriend?

My GF has a bisexual or lesbian friend. Her friend is nuts. She is one of those people with absolutely no life at all. She spends all her time on MySpace and Facebook and has no job. She always calls my GF and talks about her drama. She even sends her nasty messages (damn she is ugly) and she tells my GF that she should dump me and get with her. The way i see it is that she has no respect for our relationship. It is the same thing as if she were a man flirting with my GF. My GF even told me that she grabbed her and gave her a kiss on the mouth. I would like to grab this girl and slap her around. But i never met her. My GF said its no big deal, And she even thinks its funny. Does anybody see a problem with this picture? Would you be mad?