Teenage obesity

I would take your daughter to a nutritionist and start her with a completely new diet.  It might be the case that her body doesn't digest certain food well.  I would also take her to an allergist to make sure that she doesn't have allergies.  Also, enroll her in a sport of her choice, and encourage her (don't push her too hard though) to work hard at it.  I think that with these things, she will start to lose weight.  Good luck.

Start taking regular walks with her. Just for short distances at first, just to get the hang of doing some sort of physical activity. Try to make this into a regular habit, and turn it into a quality time with you.

If it doesn't reduce weight, you will still have gained some great time with your daughter, and she will retain her flexibility and movement. But my guess is that as she grows stronger, some of the weight will be lost, and you will both feel better.