It's good you are concerned about your friend! Well things you could do with her to help her would be instead of going to a movie and munching on snacks, go biking or roller blading. My friends and I go biking all the time and it's really fun! You can also go to the gym together, play some games of basketball or whatever other sport. Just try to add some exercise into her life, and stay away from fast food restaurants! Good luck! :)