How do you get over someone you really liked (bordering first love)?

I will try to keep my story in a nutshell. Last year, as a junior in high school, I met this sopre girl in my honors chemistry cl. I never really talked to her until around the second semester of my junior year. I never really knew her until we started talking over Myspace from time to time. Over time, I found that we had a great deal in common and that we are very similar people. So after becoming her friend for a little while, I started to like her as something more because of our compatibility. But, because everyone I've ever liked has only seen me as a friend, I was unwilling to put myself out there and express my feelings. However, when I found out that she actually felt the same way towards me, I was overjoyed. We went agreed to take it slow and to get to know each other better first. Things were going great until the summer of 2009. She had a history with a guy she used to really like. For awhile, the two of them didn't interact much because of something he did. He said he "loved" her and was very persistent in trying to get back into her life and somehow eventually did before the year ended. I was crushed when I found out in June that she liked him back too and that she liked the both of us. For awhile I didn't know what was going to happen. It was a weird triangle situation now. The two of them started spending more time with each other when the new school year started but she still never said who she liked more. She claimed that she just sees the both of us as just really good friends but I knew she liked him more. For the longest time, I never got any closure from her saying that she wanted to just be friends and it felt like she strung me along for months. Now, she admits that she likes him more and I am angry for the fact that she could've just told me a long time ago to save me the pain of seeing them together and not knowing if they were just friends or something else. I would've just moved on if she had given me closure. How do I get over the first person who actually liked me back after she basically broke my heart by rekindling with an old flame and not telling me?