Jesus, what's up with your kids nowadays and professing your love everywhere? Where do you think that's gonna bring you, you already know she has a boyfriend and she will not do the same.
The best thing for you to do is to treat her like she doesn't have a boyfriend. Act the way you'd normally act, but looking at your post, it doesn't seem that well off either.
Get her number, get her on a date, have fun with her, if all goes will, move in for a kiss. If none of that works out, well guy, she wasn't going to end up with you anyways.
But to tell her you like her is like handing over you nuts in a bag for her to do anything she wants with. You're already desperate because you barely met this girl and you already "like" her. The most she should get from you is a little interest since you barely know her and the best you can do is "she seemed to talk to me more than anyone else in the group."
The help you need won't be easy. You have to change your whole person in order to improve your life for the better. But as a start, don't be so desperate and head-over-heels for a girl you barely know. You could live without her. Just chill off and treat her like any other girl if you really want to move on in there. If she's loyal to her boyfriend, which she probably is, it isn't going to work out. But it's better than just giving her something she may or may not want.
