Why not just sit down and write your mother in law a love letter telling her of all the various things you thought about her while you quilted her quilt? Tell her about the various blocks and why they meant a lot to you - for only her. Tell her many thing/reasons that you love her & also love it that her son is your husband. Your gift of the quilt is simply a way of expressing love. Perhaps she has very little self confidence - boost her up!