Since she bought the fabric it sounds reasonable to me. I admit I'm a wus and undercharge invariably. But what can you do?
For the toddler princess apron I made "from scratch" I charged $15.00. She gave me $20.00 and loved it. Realistically I spent about an hour making up the pattern and cutting out the pieces and another hour putting it together. But could I really have asked her to shell out $30.00 (plus the cost of the fabric) for a toddler's play apron??
If we depended financially on the money I make sewing I guess I'd look at it differently but I can't charge what I wouldn't pay.
JMHO