Maybe the best way to go about this is to sit down with her and make it a combined effort to eat more healthy and start exercising TOGETHER!

That's the key word....TOGETHER. Making a habit of going for walks together every day...sharing in the shopping and preparing of the healthy meals TOGETHER can make all the difference in the world no?
Doing the things together that will help make you both healthier is a great way to stay on track and to feel connected!
Wishing you both well!

sabby