What's up with the distant girlfriend?

The first thing I would do is ask her who it is that keeps calling and texting her, but be nice about it, at this point it could be any one. Tell her how you are feeling and what your fears are. It sounds like she has been through a lot, and if the two of you are as close as you think you are she is probably looking at you as the one thing in her life she doesn't have to worry about. It sounds like you are her rock, and she needs you. Tell her that she is not going through these things alone, and that you want to help her, even if it is only as a shoulder to cry on. She may not be aware of the fact she is pulling away from you. Just remember that while she deserves your honesty and support, you deserved the same from her. Talk to her about these things. Let her read what you have said to us. It will help the both of you.