You say she is a quilter so she should really know better, but be that as it may, even though you have already said yes, you can always add a "footnote".
Tell you you will be happy to make 2 more quilts for her for $20 each IF she supplies the fabric and the batting. Be sure and tell her how much fabric and batting you will need to complete the project.
No crime in that! She may rethink it and decide to do them herself. Or she may agree and at least you won't be out any $$, just your time.