| You can provide negative feedback on the seller. Might not help you now, but at least others will know you were unhappy with your dealing with this person.
I also had a similar expernce. Won an auction as the highest bidder and left geoexpat messages for the seller. The seller gave me negative feedback as she was unable to contact me. She didn't know how to use her geoexpat private messaging so she had neither read any of my messages nor messaqed me. To make a long story short, after numerous emails discussing the fact I had won the auction at a certain price and her asking for more money, I ended up paying 25% more than my winning bid. The seller added a neutral comment saying we had completed a deal (I had asked her to rectify the negative comment). Should've been positive feedback added but not much I can do.
To be fair, the seller (and your seller) probably wasn't aware she could have a reserve price, and was not overly familiar with the website and private messages. However, if I had bid twice what she expected to get, and then offered less, I'm sure she would have insisted on the bid price.  | 
