I like toverly's answer.
You could also announce that you will only work on quilt tops that are flat, corners are square , and seams are fairly even. Quality to be determined by you. Tops that are wavy, uneven, and with open seams are a pain to work on.
Or if the person insists , charge triple for aggravation!
You can announce your practice days are over and you are only doing quilting for pay now.
Although most of us try to get more skilled the more we do, that is not the point.
it also sounds this person is not getting much better as she goes along..
It sounds like A is choosing to ignore subtle hints.