Should I forgive her, or tell her to get out of my life?

Last night I had a friend over and we were drinking. She got extremely drunk and starting hitting on my boyfriend of 3 years. Then she proceeded to sit on his lap the whole entire night and not let me spend some time with him. Then this morning my boyfriend tells me that she also kissed him. I dont know if i can trust her anymore and I dont know if I can even be friends with her anymore. What would you do if you were in a situation like this? I just dont see how one of my so called 'Best friend's can do this to me and think that i would be ok with it. I am so not ok with it! What should I do ??