What did you do for 60 hours if I may ask?

Sex+sleep+being intoxicated+eating=60 hours? Really?.. I find it hard to believe. You must have been talking with her a lot to fill the remaining hours. I wonder if you are in reality attracted to her, because you did spend 60 hours back-to-back with her and not just 2 hours of drunken sex. I think that you might be deluding yourself. You appear to somehow feel entitled to being with a slim girl as a reward for putting yourself through dieting (be careful, by the way, because most dieters not only regain weight but gain more that they lost, in the long run, so you need to make sure that you are eating enough and exercising; fat is essential, too, to keep you feeling full and to avoid spooking your body even further, or else it might react by gaining weight, being frightened and in a crisis mode). But look around, and you will see happy couples with one person slim and the other person, big, both women and men. That she has gained weight may be due to a number of reasons and in no way means that she does not take good care of herself or is otherwise inferior in any way. Most people, according to reports, do not look the way their pictures on the dating profiles do; she simply is no exception. From now on, make your first date a coffee date, but with this girl, think carefully because the record of spending a whole weekend with her without leaving house argues in favor of the hypothesis that you do like her a lot, but simply have hangups because of your idea that your sacrifices (dieting) need to be rewarded. 60 hours is a lot to spend with a new person non-stop. Actually, even with someone you know well, to be in the same place for 60 hours might be tough. So think through this one carefully. I would simply tell or text her that tomorrow you have a commitment and cannot meet with her to buy yourself some time to think about this.