Yeah dude, seriously, just like let her know that you're not interested in that type of relationship with her. There's nothing wrong with that. And on a more worldly note, you won't look like a jerk to all of her cute friends. You also won't end up causing damage to her that way. But if you want to cause harm to her, I hope she ends up losing a bunch of weight, and getting really hot and develops an awesome personality, and then gets you on Jerry Springer on one of those "I used to be fat but now I'm PHAT" shows in a couple years, and you'll be all white trash and she'll be all pretty hot and tempting, and you'll be like "Dang. That stinks" and she'll be all "yeah. That does. But I forgive you.. gotcha!" and you'll be like "dude, why are you so mean?" and she'll be all "Safety" and fart in your mouth. And you'll never wash your mouth again. You make me SICK!