Since you need extra on three sides (or all 4 sides if you wanted) I would add an extra large border in QAYG style. If she is paying you to fix the problem, I would find a print that matched the quilt and add the fabric on both sides by cutting 8 inch wide strips of top, batt and batting. I would place the top fabric on the quilt top edge, just inside the binding,(right side down) place batt strip on top of it and stay stitch. I would then add the back fabric strip to the back( right side down to the quilt back) match the edge to the front and sew just inside the stay stitching line. I would the smooth all the layers outward and it would be ready to quilt. I would do the other side in the same manner and then the bottom section. When finished I would rebind the whole quilt again with a wider binding. A ruffle would also work, it is up to you and the customer.