If you really enjoy quilting for others, tell her how much time it would take. Then I would use a very simple pattern, such as Trip Around the World or Stairway to Heaven with larger squares. 5 inch squares would make a nice pattern, and fast. D9P quilts are easy and fast and look fascinating. Amazing Jelly Roll quilts are easy, and look very complicated and you can cut up your own fabric for the strips.
Then see if you can use fabric from your stash. I mean something that you've had around a while and have used in more than one quilt already, and really want to be rid of. I have lots of that around.
Then get at least 50% of the cost up front. Tell her it is to purchase supplies. And don't be too cheap on the cost!