Charge what you feel is appropriate, especially if she can afford it. I live in NW Ohio, and there is a quilt auction every year, where the prices are routinely over $1000. In the Amish country of north central Indiana, they run about that much,, also. I recently wnet on Judy Martin's site, whre she was offering some of her quilts for $1500-$2000 to sell them. Just rmember that your handmade quilt is probably worth every penny, because of the love and care tht you put into every stitch.