What do I do in a situation like this?

I met her a while ago through a friend, started out as texting. Eventually we met and she stayed the night, we were awake til 5 in the morning just talking and flirting with eachother. I even made a few moves and had more than plenty opportunities to kiss her, but I chickened out. It went on like this for a while, long phone calls and slot of 1 on 1 time with her. I honestly think I fell in love with her. I recently came to find out she has had a boyfriend for almost a year. I never thought to ask because she never talked about him with me or even a hint. That destroyed me. I don't know if and what I should tell her. I'm leaving for the military in a few months and feel it would be greedy of me... But I've never felt this way about someone, I'm simply always happy with her no matter whats goin on in my life. Someone help? And no bullshit answers please thanx.