She know's the risks. When you hang out with her make sure it has nothing to do with food. Ie. Going to the mall get a drink that you can carry around instead of eating at the food court, go to a coffee house. The less food is involved when hanging out the more she'll be willing to hang out with you outside the house. It's not your job to do anything but be a good friend. You could also talk to your therapist about it as it affects you as a friend.