Please don't be hurt by this SIL as she is ignorant. Speak out and tell her about your workmanship and the expense. That would be a good lesson for this person to learn about quilting.
It is too bad that crafts of sewing, knitting and other handwork are no longer being taught to the next generation. Most would rather just buy things from China. I remember when something made in China was so cheap and you didn't buy it. Now everyone wants that made in China product and it still is cheap. Show the woman the dif between store bought and handmade. Perhaps you can instill in her a healthy respect for something handmade. I had a gal stay here so she could finish her teaching degree. One day she asked if I would repair a small hole in her panties. I asked her if she couldn't sew herself and what she would do if missing a button on something. I did not repair her garment. But I was shocked!