It looks like there isn't any quilting in the area where the fabric frayed. It allows the fabric to move and pull during washing. I would tuck under the places that have frayed and do some topstitching to secure it. Then I would do more quilting all over....maybe using a deco stitch along the seams, they certainly won't pull loose then! I use a deco stitch along the seams all the time, gives it a crazy quilt look.