I wouldn't want to see the holes in it, if it were my quilt. The sashing seems to have the worst damage and needs to be changed out, but it would be very difficult to find old blue fabric that is that soft and worn. What you might do is remove one row or one column, and use the sashing pieces from it to switch out the real holey ones. (Making the quilt smaller.) Then the tiny holes in the white part can just be darned with something white behind them. I've repaired lots of quilt and this is what I'd do. I also have declined repairing some that would have taken the rest of my lifetime to repair.
You have only shown us a couple of spots on the quilt that are badly damaged. If the damage is more overall, my idea won't work. In that case I'd just remove the butterfly blocks that are still in good shape, and put them together some other way. You'll still be keeping a part of your grandmother's work for your mom to enjoy. New sashing with 30's reproductions would be cute!