If you didn't quote a price before hand it is going to be difficult to charge a fair price now. Total up what the cost of all the supplies and add a reasonable amount for your time. Reasonable for her not for you because it will be too costly probably to pay yourself what it is really worth. Few people really appreciate how long a quilt takes or the work that goes into one. The last time I made this mistake, I asked that they donate an amount to a charity in my name. They donated $50 which was okay with me (not nearly what it was worth) but the charlty appreciated the donation.