Just finished the thread... I tend to agree with the opinion that your girlfriend's weight is not likely to be the real difficulty here. For one thing, it didn't seem to bother you previously. Also, unless her essential musculoskeletal build is super-tiny, or your estimates are way off, she isn't much overweight. I'm 5'2" and a solidly built 130 pounds, am considered very attractive, and get lots of attention and flirting (whether I want it or not!). Those are very similar proportions overall to your description of your girlfriend's.

So... I think what else you can do is, consider why, after 2 years, something that isn't new is suddenly a problem. What else is going on here? You note that she "isn't sacrificing anything." Is there a reason aside from weight that she should sacrifice, i.e., do you perceive her as selfish generally? Or as having some other character flaw? Obviously these notions are total shots in the dark, I just hope they may be food for thought.

Good luck with this.