I agree with Tashana. On the label you could reference your mother like "This quilt was to become a loving memory for a daughter by her mother, but was finished by the daughter in loving memory of her mother." You could insert your names and approximate date started and then the finishing date. Leave your mothers stitches in and finish with yours. I wouldn't rip one stitch out. Every time you look at that quilt you can point out to everyone which stitches she lovingly created for you. I would look at each stitch as a gift from her heart to yours.