It is beautiful! While the friend paid for the fabric, she did not 'commission' you and she knows you are a beginner.
Leave it alone. If you think you have to tell her then fine but I'd just leave it be and see if she says anything. You could always drop a little hint about how much you learned about fabric while working on the quilt!
I walked away from three beautiful yellow and gray fabrics at Joann's for the exact same reason. As it approached the selvages the pattern veered off a good 3/4" to 1-3/4". When I mentioned it to the gal cutting the fabric she said, "Well, it is what it is do you want it or not?" I was a little peeved at her comment to tell the truth.