跟她讲you believe you were deceived and that she acted in bad faith

Then, threaten to file written complaints with her agency, the state real estate commission and the local board of realtors.

上边的是网上抄来的，试试看，不要轻易付全款。可以找当地律师咨询下，发个律师信过去最好。没准她攒了不少complaints,就算了呢。也没准你们因此可以商量个低的价格。最差无非是你多付一些律师费