is there something wrong with this?

I don't want to come off as one of those jealous insecure girls because I'm truly not. My boyfriend has friends that are girls who I get along with well. No issues there. However, my best girl friend is so flirtatious that it's sickening. She sat on my sisters boyfriends lap until he kicked her off (which didn't take long) when my sis went to the bathroom. Then she flirts with our other friends guys (not boyfriends, just dates). She grinds all over other guys even when she has a date at the bar. She has zero boundaries. She flirts with literally everyone and everything. I do not want to invite her out to my boyfriends birthday this weekend. We will all be drunk at a club. Does this make me a bad friend? Jealous freak? What do you think?