Depending on age, in my opinion, they may be permanent. Is the quilt completed? What has worked for me in the past when doing those type projects, is to use liquid dish soap. Sometimes some hand rubbing the areas together has been needed. I have generally only had 'tops' to deal with at that point and could usually manage them in the sink. If larger, use the bathtub. Fill with warm water/dish soap. Let soak for a bit, do some rubbing if needed. After wringing out as much water as possible, I lay towels then the piece on top and roll to absorb as much extra water as possible. Then air dry on an indoor clothes drying rack. If after all of that the marks are still there - enjoy the charm and memory of having your mom's work.