Can you tell if she blended fabrics in the top? 1960's it was not uncommon to have cottons and polyesters mixed in a top so it is possible you had some shrinkage in the cottons and none in the poly or poly blends if there are any in the top. Edited to add you can also try blocking the top. most instructions you find on the net are for already quilted quilts but the same principle applies. Google "how to block a quilt top" and you will get loads of hits.
A lot of imperfections can be quilted out. My lone star had a "A" cup volcano in the center that quilted out no problem. So depending on where it is no longer laying flat this may not be too difficult of a hurdle to overcome in completing the quilt. Would love to see pictures.
Last edited by feline fanatic; 09-02-2015 at 04:35 AM.