I've watched a couple of documentaries (including a YouTube homemade documentary by a Mennonite resident of a nearby Amish community) and they all seemed to say that the Amish almost always use mass produced quilt fabrics. The difference is based on whether the woman is making it for her family or for trade. If it's for her family, in many Amish communities, she will buy fabric to make her dresses & will use the remnants to sew quilts. If it's for trade, she will often buy brighter colored fabrics just for quilting as they know that's what most tourists desire to purchase.