Years ago the labor was always double the material costs, but I believe with inflation that method has gone out the window. I believe minimum wage is $8.00 or more dollars an hour now and you are not doing minimum wage work when you make a quilt.
But I would definitely make sure she does the following-
1. Furnishes more than enough material to complete the quilt or if she wants you to furnish the material have her advance the cost of the material, give her copies of the reciepts if she complains about the cost.
2. Gives you a healthy down payment for your labor and if you send it out to be quilted have her be in charge of that and responsible for those charges. (Don't want to have it quilted and then have her complain about the way it is quilted.)
3. If she doesn't like the approximate price you are quoting for materials and labor walk away and let her find someone else.
Good luck with what you decide, but definitely don't let yourself be left holding the bag for time and materials to make a quilt that she may decide is more than she wants to spend.
Longarm
Longarm