Help. Shy girl winter formal?

I started talking to this shy girl and she is shy and i cant realy get her to come out of her shell at all and also the winter formal (sadie hawkins) dance is coming up and i want her to ask me but shes really shy and i dont think she will. I have kind of brought it up to her subtly and i know she wants to ask but shes really shy. I want to go with this girl but if she doesnt ask soon, it will be to late. pleseeeee help.