Girls aren't. But enough are that just about everyone has met at least one. For whatever reason, these girls have especially absorbed the idea that women are only to be viewed as competition, never as friends, that male attention is the most important thing, etc. LKH, for instance is definitely one of these. I knew one too. But I also went to an all-female college and didn't meet a single one there. It's easy to start thinking "ugh, girls are like this!" when you've had enough bad experiences, but I'd caution against it, since, well, that's also what these girls tend to believe (both Anita and the one I knew, for instance, both thought all women were two-faced catty bitches) and it might well be the first step to becoming like them and viewing all women as potential enemies and men as the only company worth having.