I don't think you can convince her. It's her health and her choice and she may be resistant to a small person telling her how to manage her health. I know I wouldn't have been interested in hearing it. I know you are coming from a good place and want to help her. I am sure she understands her diabetes well, if you want to give her the book as a "love" gift that might be the only way to go. Evne then don't expect instant results you may unintentionally be hurting her feelings so be careful where and how you tread with this one...