I hope you ended up having a good Thanksgiving with your girlfriend. Sorry to hear how things are not working great at the moment. When I was first coming to terms with how I felt the hardest person to talk to was my husband. He is the one I love most, yet I just couldn't seem to turn to him even though he so desperately wanted me to, he needed me to, at the time i didn't realise that my depression was affecting him as much as it was me. It took time, probably a few weeks, before I finally managed to talk to him about some of the things that I needed help with, the rest of it i have either shared with the HW memebers or kept to myself. There is something about sharing with people that you don't know, that wont judge you and that can understand what you are going through (even when the problems are different) that makes it a little easier to open up. Knowing that you will never have to face the people you talk to can make it much easier - so if you can make the sugestion that she visits the forum - do it. We're all here.
My husband tried to 'fix' everything at first, and that just made things worse, I felt that I was burdening him, when really I just wanted to make him understand that sometimes it is something specific that gets you down and other times, well othertimes it is absolutely nothing - and trying to explain that nothing in particular is getting you in a state makes you feel quite stupid when someone is determined to find out whats up. I found the worst thing is when my husband used to say "Well, it must be something...", now, he just listens, or gives me a hug, or space etc - he is being really great by learning to judge my 'moods', while I am learning to deal with my issues, past and present.
You do sound like you have done everything you can to help. Letting her know you are there in an unpressured way is the best thing you can do, hopefully she will open up to you or a friend soon. It is within her power not to be like her own mother, maybe she just needs some time to realise it.
Good luck and keep us posted.