So very kind of you to work on this project for her. I think memory quilts are inherently a hassle! I did 3 lap quilts for someone out of her dad's shirts (western style but not all cotton) and his "work" pants--poly blend and cotton khakis (he was farmer). Had to deconstruct the shirts (she wanted some pocket pieces) and the pants. Plus she wanted 3 different designs--but since each had to have at least one of the shirt pockets on it I had to keep fairly simple patterns. Luckily I did not have to stabilize any of it.
Then her hubs wanted a wall hanging with his alma mater--had a flag that he wanted the center pc with logos out of t-shirts around it--but was short on t-sheets, etc.Plus he really didn't want to pay the price I needed. We finally settled on something that worked--but the process was a pain! Hardest was for my step MIL--after FIL died she instantly donated all his clothing before I got a chance to say I'd do memory quilt. Later she was at their lake house and found a swimsuit, a rayon shirt, a t-shirt, 3 knit polo shirts (the slinky kind of knit), and a tighted knitted fleece pullover and asked that I use those! Lots of stabilizer, plus addition of some cotton fabrics to make a carpenter's star. The hardest was the darn fleece--it was a Patagonia pullover meant for outdoor wear and hard to sew through. I've sent left the t-shirt making business and only make for family.