Has anyone mentioned this yet? Ask your "friend" if he's having some relationship with her. Even if he's saying yes or no, try being her friend and get to know her better. Sooner or later, if she dumps your amigo, you can have a chance....
Ok, not really like that. I once had the HUGEST crush on a girl that moved at the same time as me (both of us were seven). WE saw each other often, but it started going on less and less each year. I even talked about it on the forums, and one day, one of her so-called "friends" asked me who I liked in the class. I thought she was trustworthy, so I said her name. You know what happened next? She announced it on a school dance, and she left dissapointed. Guess what happened next? Her "friend" then said it was my idea to announce it. Her "friend" was seriously jelous that I liked her, because of the fact that I'm a favourite around the school as the jester. It got worse: her friend made her brother spread rumors (I hated that child ever since), threw eggs at her house on Halloween, and worst of all, they even hacked into her msn and displayed her dp into some pornographic shot (I wasn't there, but she was crying when I got to school and it was on the announcememnts). She finally moved and I seriously missed her. I looked for her address for almost 6 months, and finally, one of my good friends, happened to have her new msn and we ended up meeting up! She was pretty happy to see me, and we started too see each other more often, until about a month ago, she said she got a boyfriend. I was jealous, and she didn't know it. I haven't talked to her since, but I just want to call her when the time is right...
That's a weird story. Why should you bother listening? Just start some good friendship with her. It's like that one episode of Family Guy, when Brian had a crush on Lois: "We should cherish the things we have now, like our unbreakable friendship".
Well, try it. I hope it helps...