OK I was writing my comment while more details came forward. So you made the quilt start to finish from clothes and it sounds like your client doesn't know anything at all about quilting or even sewing for that matter so she is definitely upset over the shops comments because she doesn't know any better. Oh brother, what a predicament. Like I said above, the shop has sewn seeds of unhappiness in the customer and now she probably doesn't know who to believe. As expensive as the shipping is, I really think you need to offer to pay round trip shipping for the quilt to get back to you so you can fix things and carefully inspect all the seams. I realize you are operating at a loss by doing this but if you want a happy client who will not spread bad reviews about your services you need to make this right. Another option is to find a shop, quilter or guild in her area so she can get a second opinion. The shop certainly made things sound worse than they appear in the pics you posted. And I understood your post to mean that these pics came from the shop where they said the quilt was lacking in structural integrity. I just don't see it lacking structural integrity from those shots. Yes, the stitches are unregulated and look a bit large and yes there are some untrimmed threads, but unless those quilting stitches are 1/4" or bigger (what so many refer to as "toe catchers")and untrimmed threads are removing several stitches of quilting with a little tug, I think the issue is aesthetic not functional. To truly know if there are structural issues, have her pop the quilt into the washer and dryer. If it comes through the wash still intact, she has her answer and if it doesn't you will have your answer.