oh katie! I am so very sorry. But when I read your post I had this really, really strong sense that it was not meant to be at ALL and something is protecting you right now. Please have faith my dear.
However, if this woman is already waffling, she would have been a nightmare during the process. The whole thing is hard enough, and frankly, contract or not, either party can back out right up until the closing date. Good riddance to her. I really think she would have messed with you all along the way. Something better (with a better seller!) will come along!
Oh, Katie, I'm so sorry. For reasons we do not yet understand, this is exactly what was meant to be! This was definitely not the place for you. The perfect place is going to open up for you at exactly the right time!
Katie, I am sorry to hear this seller has been messing with you. Real Estate really is such a battle, especially in NoVA right now. To second what everyone else has said, this was not meant to be, but something better will come!