I had a similar experience with an overweight coworker. She was huge and lost a lot of weight through bypass surgery. She was one of those chicks you'd see and think, "man if she was slim she'd be pretty attractive" (she had a nice face). However, her attitude was that she was now hot because she lost weight, not realizing that, yes, it was an improvement but you still have a long way to go.
She started hitting on me (winking, offering rides) and I would shudder just thinking about seeing her naked, uuggh...