You wear the shirt with the condom on the shoulder. That will let her know that you are looking to acquire a mate and she will commence the traditional mating ritual. You'll then need to fight off three death-badgers sent from the eternal flame. Once you've completed this task, you'll head into the Shrine of the Silver Monkey. Put all of the pieces together and you'll score the chick.
No but really. There's nothing you can do. Friend zone is a horrible horrible place to be. The worst part of friend zone is that she knows you're into her, and she'll keep you in said friend zone.
The only thing you really can do, I think, is tell her how you feel. If she responds poorly, you lost a friend... which in my opinion is better than being stuck in forever friend zone... especially if you're hanging out with her and some dude she's boning.
If she responds positively, then you win ultimate victory.
I think she'll respond negatively though. Perhaps you're the kind of guy that will settle for just being in her presence though, in which case you make my penis wilt.
There is another alternative I suppose. You could pull off something all romantic and shit but not too romantic where it's obvious how desperate you are... just something the two of you do. You can gauge her interest a lot better in a one on one situation without other friend influence.
But really, I think you're fucked. Try telling her you frequent an online community. That'll get her moist.