I think I would let the lady know that you probably need more fabric, for borders and binding, so that she can get more to you before the source is gone. If you end up with too much, oh well....
However, I wanted to offer a pattern idea for squares. I made this quilt for a Boys'Ranch about two months ago. I wanted to use ten inch squares but didn't have enough fabric, so I ended up with 9 inch squares. With a bit of math, it might help you to figure out if you have enough fabric.
Or maybe someone who is good at that stuff will be able to tell you a real answer.
Dina