I've had some success relaxing shrunken sweaters by soaking them in a tiny bit of conditioner--always thought it would work well with a quilt since it would make the fibers relax.
Think your quilt is lovely and wouldn't change a thing. Maybe you should just pretend that it looks exactly the way you intended and your MIL will be thrilled. It's all in the marketing!
Take care!
Carole
Marlton, NJ