How do I keep my mother motivated to get healthier and more active?

My family has heart disease in our blood. Mamma has changed her eating, and lifestyle to try and loose weight. I want her to be around a long time. She has been walking with me on the trail, and eating better. how to get her more motivated, and encouraged to keep going! How to I get her more involved? More praised for her effort, and congratulated. I want her to keep going though, and get her healthier!