As someone who used to write and who knows how hard it is to find a place to do it where you can use the space you need, I completely sympathize. I would not have moved. As it is a public spot, first come first dibs. As a professional she should know this. Would she have packed all her crap up and moved for you? Seriously doubt it. The amount of time I am asked to move is not important.
So, let me ask, as photographers would you pack up all of your stuff and move when someone "asked" you to so they could use the space, or would you say no and keep shooting until you were done?