I kinda now exactly how you feel at these moment, I was playing the role of the gilfriend who had depression for a loooong time, sometimes I get sad again but there is nothing no one can do. Or at least that is what I think...
My boyfriend of almost 4 years had been there for me all the way long, everything started bc I suffered a horrible expirience meanwhile I was in an exchange program in a whole new country way too far from home, it was terrible and I really tried to suicide several times, now is not so hard but back then it was just miserable life... but even with more than 4,000 miles away and just a few months of relationship with my boyfriend, he been there really help me more than he thinks, a few months ago when I finished my all week therapy season he told me that sometimes when I was depressed he thinks that his presence or his words didn't help me not even a little bit maybe because it was so hard for me to be open and talk about it even when I tried, or because even when I smiled he knew I wasn't really happy but there is somethings we can't handle it but always always been with someone helps.Perhaps, maybe at this moment you're confused or my story does not help you at all but I just want you to now that only the fact that you're there for her helps her so much more than what you think or what she can say or express right now, just do not push her, no matter what the situation is or, I know maybe you despair or wanna give up sometimes because is gonna be hard, but give it time, because only time sometimes helps us move forward.Hope this can help you, also try to convince her to go to support groups, is hard but it helps to see us that we are not the only ones in this.