Hm, it's a hard one, but I guess one way of going around it would be to talk to this girl you want to ask out, get to know her as much as you can, whether this be hanging around together or in a group, you could always try to find out who she likes? Gaining confidence to ask anyone out is hard for fear of rejection, but once you've gotten to know them well, you should be more confident to be able to ask her. There's many ways you could get around it, you could ask her straight out or you could be more casual about it, like asking her round to your place, and seeing how she feels about you, the worst thing she can say is no, and there's going to be someone else out there for you if that happens, so just go for it, you don't know until you try?:)