It sounds like the two of you broke up, so having a talk with her now, is a little too late. I’m sure you’re right that there is more she hasn’t told you — but again, it sounds like it’s past the time to have had the conversation.
Fill me in a little further — how old are you both, and how long have you been living together. Also, you mentioned that the two of you were in a “desperate situation” for money — how did that happen? It sounds like that’s an important part of the problem, so give me some more information and if I can help you further, I will. 😉