My ex girlfriend and I have been avoiding each other for seven months since we broke up, and at prom the strangest thing happened. At prom i had received at tip off from her best friend (she tells her everything) to ask her to dance the next slow dance with her. When the time comes i ask and she excepts which i was really surprised at, it was the last dance of the evening to top it all off. Now we are slowly getting back to being friends, and a mutual friend of ours keeps smiling every time she see's us together like she did when we were dating. The part that really makes me curious is that the mutual friend knows something about my ex and refuses to tell me no matter what, all they'll tell me is that it's about me, I personally want her back but I'm pretty sure that wouldn't happen. What should i do?
Sorry for the long post, please give any additional ideas and votes with your comments.
Sorry for the long post, please give any additional ideas and votes with your comments.

You should not blatantly ask for her back, but aiming in that direction may be the most reasonable.
I'd guess she had some random fling during those 7 month and realized you're more to her liking than she actually thought.
Like, serious, your friend "knows" something about your ex that is about "you".
And suggested you ask her for a slow dance(oh wonder, she accepted).
And looks at you 2 with the happy smile of a successful matchmaker.
You need someone to hit you with a sign? Men :P
On an aside: Why did you break up in the first place and on who's initiative?
If you broke it off and she wants you back, well that is up to you.