I'm so sorry that you are having these issues. Quilting for someone else, I believe, is tricky. Most non quilters have no idea of what goes into making a quilt. Your quilt really looks beautiful. I FMQ my own quilts on my DM. For the life of me, I am unable to get equal length stitches. However, laundering the quilt pretty much disguises those unequal stitches. Using different fabrics, I believe, would also be difficult. I have also had some quilters who work in shops be very judgemental and critical of almost everything. You have stumbled into a really difficult situation. I do agree that I would have her send the quilt back to you so that you may see what you can do to correct any open seams and bury threads. I have also found that with a quilt this large, it is easy to miss tales on the backside. Good luck!