Who to Ask to the Dance?

I'm a Sophomore at a rather small high school, and the Freshman-Sophomore semiformal dance is in two weeks. I've been wanting to ask one of three girls, but I'm not sure who to ask, how to ask them, or if I should ask any of them at all.

The first girl is a girl I have always kind of admired from afar since Freshman year. She found out that I liked her towards the end of last year, so I stopped liking her. This year, we talk to each other every so often, a couple times a week probably. I'm thinking of asking her as a friend and seeing how it goes, but she mostly hangs out with the popular girls, who I rarely talk to just because I don't know them so well and I've never really wanted to except for her.

The second girl started going to my school in January. I was confident enough to be the first person she talked to, and I became her first friend. I started talking to her less and less because she got her own group of friends and didn't need me. Now, we don't talk at all, and, when I try to talk to her, I get a vibe that she doesn't like me.

The third girl is also new at my school, and I talk to her every day in the one class I have with her and her twin brother. She can seem stuck up at times, but she's usually nice to me. I don't know much about her though, but I'd ask her just as a friend.

So, which girl should I ask? Should I just go alone? Other things? Thanks for your help!