What a bummer and I hope that she contacts you that she just forgot the part.
I hope everyone who reads your story or hears about it from you learns from your hard learned lesson. YOU have to be really careful when buying from anyone selling second hand, from the newspaper, Craigslist, EBay, etc. I work in a call center for a major corporation and I can't tell you how many times someone calls up tells me that they purchased one of our products from Craigslist or Ebay and it's not working properly or missing something. A lot of times the real owner has already called in and reported their registered product as stolen.