Hm, interesting answers, but I believe the OP for the most part is right. I have yet to meet a girl who wasn't at least a little bit selfish or self involved. The most simplest answer is. Girls are emotional. From my experience it's a reflection of an insecurity of wanting to be accepted. Whether it's from guys in general, or one guy in particular. The sluttier the clothes, the more guys that look. The more expensive the things, the more value they think they have. Even if the girl is perfectly happy with herself, this behavior could spawn from an insecurity within a relationship. It's all relative, but as I said, easy answer is girls are emotional.