Should I leave my only friend?

I basically only have one friend. She is really sweet, but she always points out how she's the "prettiest girl in the world" and that she's "prettier than me." Also things like "I'm the smartest person ever and I can do whatever I want." Childish, I know. Plus, I'm 14 and... That explains a lot! XD It really hurts, because she's really the only one I have. I am very antisocial and I hate making new friends. Should I leave her and be friendless, or stay and deal with it?