Why do only fat girls like me?

Firstly, Victoriathefirst, jump off of your high horse! Its people like you who make it seem acceptable to refer to someone who is overweight as a 'beast'. The funny thing is, I reckon that you either are or were overweight yourself, or you simply have a morbid obsession with your weight. Time to go and see a counselor I think.
Oh and for your information, it is only the shallow, bitchy women such as yourself who judge people so cruelly. If we refer to a guy as a jerk or a creep then there is usually a good reason for it, not simply their size/shape/colour etc. You see, human beings like to get to know each other before judging...Perhaps you hell-born demons should fall out of the nasty tree and hit every nice branch on the way down. It might do you some good. :)

Secondly, to the question asker, I think people are so offended about what you've said because the term is a tad harsh. I get that you've got caught up with writing the question, but perhaps a proof read might be a good idea in future. I agree that this girl has issues and is certainly not right to be attempting to cheat with you on her boyfriend..but the point is that she was just one of your examples, remember? And it isn't fair to judge and name people simply because of their size. Fair enough if you aren't attracted to them, but name calling is unnecessary.
I think hope_9 has it right though -- maybe because you actually talk to them they think they've got a chance, because most others won't give them the time of day. Or maybe you're naturally flirty and just don't realise?
Either way, perhaps next time just think before you post a question - if you use such controversial language then expect many of your responses to be about your terminology rather than actually answering your question.
I'm not sure why the skinny, 'hot' women aren't going for you...but perhaps they sense there is something judgemental about you. Most women have moments where they feel insecure, and they certainly won't want to be with someone with whom they don't feel comfortable enough to be who they are. Lose the attitude and the chip on your shoulder and you'll probably have better luck in the future.
I hope this helps...And please, please, please don't listen to people like Victoriathefirst; she is most certainly not representative of the general female populace and it is women like her who should be avoided at all costs and eventually bred out of the population. Here's hoping.