I would just tell her that you would like to make her a quilt but aren't sure if she even likes them or wants one and you wouldn't want to make something for her that she doesn't want. If she says she wants one then I wouldn't hesitate to tell her about your granddaughters quilt. She will then know that you want her to use it but not abuse it. Make sure to tell her to be honest and if she doesn`t want one you won`t be hurt.