I know what you mean.....those girls are a no-no, not because they are fat, but because usually fat girls demmand more attention, they literally own you if you are with them.
Dude, if she's pestering you then you didn't do anything wrong Penny. That treadmill line cracked me up. Just tell her to relax a little bit, I guess. Also, don't be mean to her. There was this girl in my old neighborhood that was pretty fat. Didn't see her for around 6 months, and she got skinny, and pretty. Either way, you didn't do anything too bad man.