Not sure if this will help -- is your grandmother in a wheelchair, by any chance? I sew wheelchair quilts for charity; it is recommended that these quilts should be smaller than other lapquilts, so they don't get stuck in the wheels. The recommended size is around 36 x 44, or thereabouts. (I just made a wheelchair quilt that measures 40 inches square.) Otherwise, I make lapquilts larger -- the size above (54 x 62 inches) sounds right. Also, I agree with starching. I didn't realize how important it is not to stretch bias edges when I started; starching and careful handling are very important!
You probably know that you must also consider fabric requirements for binding and backing.
Last edited by JDpenelope; 09-02-2017 at 12:11 PM.
Reason: Thought of something else