Her intention was to leave Istredd, hence one kestrel. The situation got muddled when she understood Istredd's plans, him wanting to marry her, while Geralt, the man she actually loved, was, well... hard to read at that time, to put it mildly.
There is no way that you can make Yennefer look good in this situation, because that is not the point of this story. The story is meant to cast light on the emotional state of Geralt and Yennefer, a state that prevented them from being together. There were a lot of things that worked against their relationship, their myopic view of what it means to be in a relationship being one of the factors. As I said before, Yennefer needs this debacle, as a character. It's a plot device that seves as a wake up call for her later development. She swallows a bitter pill of her own making and she learns something about herself and what it means to truly love someone and be worthy of someone else's love.
I actually like this story. Not because it paints Yennefer in a great light and she's really cool in it, but because it humanizes her.