I finally finished it and mailed it off. Hope you & your Mom like it Nicol!
Make a 17" x 65" rectangle with a buttonhole 9 inches from one end, 4 inches from the side, and add three giant buttons on the other end, first one 9 inches from the end, 4 inches from the edge, and add the other two spaced 4 inches apart towards the middle.
Though the curling of straight stockingnette makes a nice rolled border, I may try this again with non-curling edge stitches as I knit it, or pick up & knit the edges to do so. Either way, this simple wrap feels fabulous - just the right amount of warmth to take away the chill, and a little drama to boot!