I think this subject has come up before. The amount is never enough, really that you would make off of makig a quilt for a friend. It is a labor of love in the end. I would try for at least minimum wage, if you can get it from her. People just don't realize what it takes ot make a quilt.
I solved the problem once with a barter. She knitted a sweater for my grand daughter snd I made her a baby quilt. I loved that sweater. She really put herself into it. It was a win win situation.