As a customer I always asked for a high estimate. In your case, you have the estimate you gave her. Get your figures down on paper so you can see the difference and if it were me, I would go with the one closest to the estimate you gave her. Say you gave her a $150. estimate and it ended up going to more like $225. 225-150=75x50%=37.50 +150=185. That's one figure. $12 (sewing per hr) or $15. (quilting per hour). take each total and figure the average. Go from there!