No idea on the name of the pattern. I just wanted to put a bug in your ear about documentation on the quilts. For the quilts that you *know* that your MIL made, put a label on the back with her name and a date range for when you believe it was made.
You may want to enlist the help of a quilt historian to determine which quilts were made by her mother, and get labels on hers too. It'll REALLY matter in a generation or two. These are family heirlooms, and doing the legwork now will be easier than in 50 years.