I have a friend problem. Please Help Me?!?

ok so i have this friend Erica. Shes kind of a loner. She only listens to the beatles, and only watches spongebob and Dragon Ball Z. She has no idea what Hollister is or who Snooki is.She texts unfunny/offensive demotivational posters to me at 3am. We're best friends.I'm kind of popular, but she doesnt seem to notice. She talks trash about my popular friends. One of my friends pointed out how annoying she is, and since then, ive been trying to ignore it, i dont want to lose her as a friend. but she says the wrong thing at the wrong time, and is hard to talk to. I'm not into gossiping, but she has NO idea whats going on, at school, pop culture, fashion, NOTHING. She asked me to take her to a mall, to show her what girls at school are talking about all the time, and is just starting to do her hair in the morning and care about her apppearance. Her parents dont seem to be all that happy about that, what do i do?