I don't think anyone is saying that she (the dev) didn't use her leverage to her advantage. We all recognize that it was the OP's fault to give her that leverage in the first place.

However in business, relationships and "karma" - for lack of a better term - are really what things are about. There are times when you should be looking at maximizing your position, and there are other times when you should be looking to cooperate in order to maximize a collective position.

Many of the people here (myself included) are simply stating that the dev displayed poor business acumen by being too aggressive in taking advantage of another's weaker position. The key being who that other person is - her supposed partner.

Partnerships need to have a level of loyalty beyond any particular transaction or they simply won't work.