Honestly I would run..........I would be very tempted to put the T-shirt’s in a bag and return them to her saying that you researched the quilt’s requirements and don’t have the skill or equipment to do a good job.....and that you just can’t stand the thought of cutting into those special shirts! Give her the contact info for some specialists......
I know someone who is making one for her own son and has sourced replicas of his shirts because cutting scares her!