All you can do is give her space and time. Either she will come back to you or she wont. If it is meant to be for you to be together then it will happen. She may just not want you to have to wait for her and have to tie you down, or she may be really scared, etc. Its got to be really tough being deployed to Iraq and leaving your friends and loved ones behind. I would say just stay in conact with her even when she does leave. Stay friends. You can let her know you still care for her no matter what and you respect her feelings. If she decides she wants to come back then you are there for her either way. Its got to be tough. Maybe she just wants to end it it could be anything. Just try and put yourself in her shoes and try and think of all the things she is going through right now. Deployment lasts a long time. If it is meant to be it will all work out in the end.
Well, at least you are supporting her. But right now, things are going to be difficult for her so let her go. Then, when she gets back, try to pick things back up. That's what me and my finance did. I missed him more and more every day but it was worth it just to have him back.