Why am I still not over her? Would she come back to me?

I was with this wonderful woman, or I thought. We made life long plans and talked of marriage and adopting her kids. She's going through a divorce and promised me I'm not a rebound. Promised me to stay true to me while in Iraq. She made me feel like I was the only one and was needy for me all the time. Until one day I was at home and she sends me a text message that she wants to be just friends to put herself through college and focus on her kids. I said it would hurt too much if she found someone new. I actually found out later she had been talking to another marine right before she left me and now dating him. She runs through my head all the time and my God it hurts. My dream of marrying diminishes and it saddens my heart. It has been a few weeks now and since then I have came to Iraq. I sent her what I thought would be a heart touching goodbye letter.