I am in a very similar situation -- except that I am the girlfriend, and my boyfriend is the patient, supportive one -- and I am completely stuck. Try as I might, I want to give you some sort of cheery answer, but I can think of nothing comforting. Still, reading what you have written makes me think of my boyfriend ... I want to be able to say anything, something that may be helpful. To that end, I will simply write what I think, and hope that it offers you at least some glimmer of insight.
Some days, it helps that my boyfriend can see beyond my boyish "flaws" and love me all the same. Other days, I simply feel ugly or defective and it isn't at all about how anyone else sees me. It is more so about how I am obsessed with acceptance, and how I have demented my interpretation -- my definition -- of what is acceptable.
If I had to express it in words, I would say that what is acceptable to me is what I think society sees as acceptable. I fall into the trap, the very same that many women of all walks do, and define this notion of "When will I look okay? When will no one judge me?" on a nigh-unreachable media beauty standard.
The important distinction here is that I take this extreme definition of aesthetics and make it my standard. A standard that I am readily disqualified from because some of my features are slightly unusual (size 12 feet, hands that I convince myself are too big, slightly wide shoulders, so on and so forth). I can never reach this standard of mine, by my definition. Not ever. It is simply not possible.
In my mind, on my darkest days, "not ever" translates to "You will never be okay. You will always be judged." Of course, in turn, this sends my mind on an even darker cascade, convinced that I am not lovable, which makes me feel that life is simply not worth living. I do not want to be unsightly, untouchable, unlovable -- alone. I would rather die.
It is easy enough for me to blame this on being transgender, but many other women (and men, honestly) walk a very strong parallel of feeling that they can never be good enough. Those women will always blame those features of theirs which they deem are the least acceptable.
As it follows, I suspect that I am not necessarily unhappy with what I cannot have. I think that I simply grew to believe that some of the harsh treatment I have been through (as a child and onward) was predicated on my failure or some deficit in my desirability. Somewhere, along the way, I began to believe that a better appearance would help alleviate some of the rejection I might face in the future. That, somehow, the more I could surpass normal in a positive way, the more value I would have -- and that fewer and fewer people would want to discard something so valuable.
None of the above is true, of course. Some of the people in my life have been selfish and horrid. These people caused me enough distress that I began to chase after the impossible, searching for an escape from the pain of not being good enough. It has become a subtle and pervasive obsession with all that I do -- the undercurrent of my life, if you will.
I can reason all of this out in my mind. I can, upon reflection, recite it to you, here, in writing. I can acknowledge that, in my current life, I have all of the love and acceptance that I need. Still, those are only words and recognition. For whatever reason, these things have never been enough to help me through my problem. I often wonder if this self-destructive malady of mine is even curable.
Tomorrow, I may forget all of this introspection. I could very well be balled up, under the sheets, at 4 in the morning, trying my best to conceal my distress from my boyfriend because I do not want to chase him away with my 379th nervous breakdown.
I don't know how to help your girlfriend get by her problem any more than I know how to help myself. What I do know is how to give you my perspective, hopefully from a similar position, and hope that you see something we do not.
I have reached a point where I believe one of the best options I have to save myself is to trust another person. I trust my boyfriend. I listen to him. He does help me. I'm sure he can and will see answers that I do not. In fact, I don't know that I could have written this honestly a few years ago.
I don't know that this will help. I genuinely hope that it does. I know it is a very difficult process for all parties involved.
I wish you the very best of luck, really. If nothing else, please continue to take care of her. If there is an answer, I am certain that you can help find it.
(I do realize that this reply is quite late, but the situation struck from such a familiar place that I felt the need to share my thoughts and cross my fingers that the TC would eventually read)