Everyone is obsessed with looks. I know I am. You can't want someone you're not attracted to. That being said, the girls I fall for aren't always the picture of perfection (not that they would have anything to do with anyway).
Also, there's a difference between being fat and being, uh, not thin. There was this one girl I was drooling over all year, and after losing weight over the summer, she didn't seem nearly as hot. Of course, she came back more popular than ever, but she didn't seem as cute to me. However, she was never really fat.
I, on the other hand, am fat, and from my experience and observations, I can tell you that most fat people of both genders aren't very lucky in love at this age. There's the occasional exceptions (I'm guessing), but if your friend is anything like me, she's probably going to be very lonely. The difference between fat guys and fat girls is: fat guys don't get used for sex. If she's that desperate for a hot guy, it might come to that.