I'm so glad you're going to make the effort to remove the stitches and have it requilted. This was going to be a very special gift, and your niece doesn't deserve to have to "settle" for a second-rate quilting job.
I understand your reluctance to confront the quilters, but I wish you would reconsider. If she is proud of the work she is doing, she will continue to work this way, and other unsuspecting quilters will also be unhappy if they take their quilt tops to her. If you don't feel comfortable with a face-to-face meeting, could you write her a letter, outlining your dissatisfaction, stressing that you're not asking her for a refund (but I think she should give you one), but that you are spending a great deal of time removing the work she did so the quilt can be finished in a more professional manner. And include the pictures - put a note with each saying why you don't think this is a good job. She really does need to know.