A lot of this depends on the guy, and on how the girl wears her weight. For instance, I have a friend that weighs 180 pounds, and she does NOT look it. She is a personal trainer, so she has a lot of muscle, which weighs more than fat. In fact, I'm not a small girl, as I'm 5'8" and a half and 165 pounds. And I've never had any problems finding guys. But because of my height, well, I wear that weight much differently than someone who is 5'3" and my weight.
I guess what I'm saying is don't focus on the number. I don't allow scales in my house so that I don't. That number really means very little, other than yoour mass versus gravity, etc. What matters is what weight you have. Is it fat, is it muscle, is it proportioned or all in one area?