Aileen, it's a beautiful quilt. We always see the imperfections in our work that non-quilters don't notice. If your grand mother is/was a quilter then she might notice, but if she wasn't a quilter if you don't point out the quilts short comings to her, she will probably never notice them. All she will see is the love and hard work you put into making her a treasure. I would go ahead and finish quilting the quilt, and then if there is time, make changes to the corner that is bothering you.