I completely agree with those who said that listening goes a long way. Asking questions is actively listening, and shows you have a vested interest in her. I had a best friend for over 25 years who was beyond morbidly obese. I could not relate to that, or to the hip and joint problems she had as a result of carrying the weight around, or to the depth of the self-loathing she had over being unable to lose the weight.
It really helped her gain perspective once we started talking about how everybody has some kind of “cross” to bear. Nobody gets a free ride in this life. NOBODY. If it weren’t this problem, it would be something else for your friend. No doubt about it. Once you see it in those terms, perspective comes a lot easier. Maybe you could mention that to your friend.