*Edit
Just saw the date on this thread, found it through google "PUA Ballroom"
How did things with this girl and dancing go?
A dance partner is absolutely invaluable.
Why not have her as a pivot? Don't worry about the "friend zone" just actually be her friend, and let her be yours. Albeit mildly flirty, and have a really valuable doorway open.
You know how when you have a girlfriend all of a sudden all her friends eye you? This is like that.. except you're actually available. In this situation you have all the draw of being the forbidden fruit without actually being forbidden!
Also it's such great social proof having a HB10 go with you out social dancing. If you can make a schedule of the local dance clubs (swing, blues, salsa etc. tend to be more social than ballroom, which is generally a couples, older folks, and competition thing) she'll appreciate you as an asset by adding to her social life. I did this with my former dance partner and she was constantly asking my permission to being her hot friends along. Of course
Delayed gratification, you have a wonderful opportunity to develop your lifestyle and skills. Girls really DO love a guy who can dance well. This is like taking a $100 now or investing that and getting a much bigger payoff.
Of course, she might just develop a thing for you, if so cool! But that shouldn't be your priority. Invest in your social circle and lifestyle man, trust me on this one. The reward is bigger than you can imagine.