Michaela I travel in similar circles as you. I have been thinking about this question and have been trying to think of a response. I certainly do ot feel criticized by my female peers generally. At least not about my dress or whatever.
I think that women can be more critical of other women then men can in general. I also am inclined to think that is in a certain segment of the population. If you are more interested in fashion or outward appearances, chance are, you travel in circles where other women feel the same. In those types of groups women seem to be more critical of each other.
I have been watching Big Brother 6 this summer and have been astounded by the cattiness among the women there. Now I do know that is not a representative sample of female society! There is a group of women that is awful to the "outsiders" behind their backs and they are friendly (at times) in front of them. That does happen outside the Big Brother house unfortunately. Two women were talking about their "boob jobs" and were poking each other and such. It seemed similar to the body building men who are only interested in themselves and others like them. Women are not as generally interested in those men as the men would believe. I suspect similar could be said about the fake "boobs".
I could be wrong.