In the long arm circle, we call those happy quilts, all the borders waving at each other. Since her piecing is so excellent, I would ask her to remove the borders. Show her, or give her a picture handout, of how to measure through the center of the quilt and make the border fit the quilt. Always sew the borders on with the quilt on the machine bed so the feed dogs can help feed any quilt fullness into the seam.
You can sometimes steam out some of the fullness, but if it is as bad as you say, they need to be removed and cut to fit and reapplied.
Lu in TN