Basically this is how my story goes she goes to my church first time I saw here was when she was at my youth group which was my freshman year of high school I will be a senior in high school she will be a freshman in college and she has a boyfriend who in which did not tell me and guess how I found out I was on a fall retreat with her and I was sitting alone and talked to one of my friends about it says she's got a boyfriend now and I was like no way and another friend comes over and says its true and I was like dang it come on and now this year months later in may of 2012 I get a message from here boyfriend on having feelings for her and he told me back off with the feelings towards her and now I and her are so so friends we used to be so close now we are not anymore and her boyfriend is a cool guy and I have only told 5 people this story and they said move on from it which I am trying to and now what should I do from this can I have help please

You back off. Leave her alone. Stop talking about her to people.

Also one more thing while her boyfriend was not with her she was flirting with me

Another reason to leave her alone. She appears to think there there is noting wrong with flirting with you while she has a boyfriend, and then her boy friend tells you to back off. That is unnecessary drama. Leave it alone.

Have you ever been in a situation like this before

When I was a teen I was in a similar situation. When I found out there was a girl friend in the picture, I was done.
I'm not fond of guys who flirt when they know that have a woman at home.

First, if you would learn to use punctuation, you wouldn't have one long and hard to understand sentence. I had to read this twice to try to get sense out of it.

Leave her alone and forget about her. You're wasting your time and setting yourself up for problems.