It really is not an easy path to walk as the patient, and I'm sure as a concerned parent it can even be worse at times.
It is typical to have periods of rage. And when one is depressed, there is just no motivation. I was dx'd about 18 months ago, and have finally managed to finish my degree. I do think I've been suffering for a lot long, probably from when I was 17 and in my last year of high school. So I understand how this affects, amongst other things, one's schooling. When I was studying my degree via correspondence, I'd give myself slack during the depressive times (I am a very rapid-cycler). I also knew that when I was feeling well, I'd have to make up for lost time.
I'd break my day into chunks. I needed to quantify what needed to be done that way, and then broke it down. Every time I could tick something off, I'd feel more motivated.

I think it's great that you care so much, and I can only imagine how much it must hurt you to see your daughter going through this.
My advice is to just make your presense and support known to her. Let her have her depressed days; rage happens from time to time, but needs to be kept in check. As she becomes more mature, she'll learn to check herself. She will eventually take up your offers of support. It's just very hard when you are demotivated; it makes you feel bad and even more depressed, like a failure.

I hope we can help you make this journey as smooth as possible