How do I deal with a friend who has bad boundaries?

She "friends" my friends on facebook even though she hardly knows them, tries to invite herself to social events when she's not invited. I've known her a long time but since the advent of facebook it's starting to get really bad and I'm creeped out. I've distanced myself from her: don't return her emails, vm messages, etc., but that doesn't stop her. I just found out she's wiggled her way into a very special get together by inviting herself. Very annoying. Yikes, I want her to get away from me and my life. What should I do/say?