What is a good way to ask this girl how I'm not dating to a dance?

Well there are only 4 things that come to my mind.One, She is waiting for someone to ask her.Two, she just got out of relationship and wants to go with friends.Three, she probably just forgets but means to do it.And 4, you didn't let her kno you into her.
:) hope it helps

If she's your friend just ask her if she's gonna be there and if she is if she'll hang out with you. Problem is she probably won't see it as romantic she'll see it as a one off just friend thing. But since you asked her about it she'll probably return the favor by dancing with you and being by your side for at least half of the night

I know what it's like to be nervous. Just build up the confidence to ask her. I mean the great thing is you have been talking to her all ready. Does she laugh at your jokes? Does she smile?
If she does then you should feel a lot more confident. she probably likes you.

Practice asking her in your mirror at home. lol It sounds funny but it may help build your confidence. Trust me, if she likes you and you ask her straight out she will be impressed with how assertive you are. Heck, she may even get really nervous and blush.

Remember. YOU ARE THE MAN, just don't get obnoxious.

And hey if it doesn't work out at least you are one step higher on the ladder of life. Good Luck!