Send her an email link to this page - she doesn't have to join to read it - then pack up the top and send/mail it back to her with the suggestion she take it to a LQS. Let them deal with her.
By the way, do you know the person she has sold it to? That person is being ripped off paying $400 for a quilt in this condition! If you speak up, you will be sparing 2 of you the "gall" (or 'balls' (?!)) of this acquaintance. She certainly had you pegged (non-confrontational) when she managed this one!
I hope you will find the strength to stand up for yourself in this case. The "loss" of this kind of "friendship" is no loss indeed!
Jan in VA