So sorry to hear of her loss.
Here's the link to the seven dress shirt quilt:
http://thethriftyquilter.blogspot.co...e-thrifty.html
This results in a throw, 52” x 64”, so extrapolating, a small queen, 80X80 would need about twice that. There's no reason why you can't just add yardage in a neutral or complimentary color, however, so the number of shirts isn't really super critical.