This is not YOUR fault. Take it back, quilting and all, and tell her respectfully that apparently her machine needs to be tweaked so that the tension is right. Use kind words. Maybe she was in a hurry or she feels that since it is a donation quilt it is good enough...she needs to know that it is just as important to do acceptable work on a donation quilt as on any other customer quilt. SHE needs to rip it out and re-quilt it is that is what has to be done. She should have one of those electric "razor" type rippers that will take out the stitches much faster than you can.