I really can't give you advice specific to your stich, but I will make some points.
1. With the discussion that happened Saturday night, about her being sorry. It is posssible there is something she wants to tell you, but is scared as to what your reaction will be. Try not to think about what it could be (I know, easier said than done)you will only make yourself angry and anxious. Keep up what you are doing because it is making her feel comfortable in talking with you. Do not approach her or ask her outright if she has done anything, it will make her withdraw.
2. Keep the communication lines open as best you can (you seem to be doing a very good job of that). I find most women (myself included) do not open up to men if they feel they won't be heard, be jumped all over for their views, or if they do not feel any kind of emotional connection or safety.
From what I have heard, the book Men are from Mars, women are from Venus (I have not actually read it) is a good book that addresses communication between men and women.
She seems to be taking on an awful lot at once, going back to school, job search, friends wedding, ect. It sounds like she is overleading herself and it is starting to form into depression (especially with the suicidal thoughts). Have you asked her if she is open to seeing a concellor for herself?
As for what to do, there really is no difinitive answer to that. I think what you are doing is working well, you are communicating better and becoming closer, although not as close as you want. BE PATIENT. Work on yourself first, the relationship will follow.
