I don't think you can blame the seller for trying to make the most out of the situation. You went to her & told her in a manner of terms that you were desperate for the shoes & would be prepared to pay for them.
If one of my customers (I sell film memorabilia) ask me to get something for them, it will cost the mmore than if I just had it hanging on the wall & they came in & picked it out. Why? because I can, its business. Supply & demand.
Your seller is giving you a higher figure to try & assess your true budget. don't be afraid to try & haggle!
you can either lay your case out (for example if you have seen another pair on ebay for less) & go in really low (say $50 above retail & then the two of you will meet a compromise, or, you can go in & say '$xxx, thats my final offer. but I thin kyou'll havea much better result with the first route.
good luck & next time, never give away your desperation! make out like its a passing fancy & that the seller will have to work hard to make you buy them.