She only wants sweet things to eat and also seems very withdrawn from any sort of activity, she constantly has a drink on the go. I have had her checked for diabetes but this has been ruled out as results were negative any ideas?

As her mom and the grocery shopper, you control what is purchased and what your daughter eats and drinks. Provide her with healthy snacks and well-balanced meals. Don't buy sweets.

You're in charge.

Agreed, she can't eat sweets if there are none in the house, or if you just tell her no, and merely serve good balanced meals.

Buy sweet fruits instead. There are many 'sweet' alternatives that does not involve junk food.

She wlil not go hungry. Stop offering the sweets and the 'yummy' food, and she will eventually eat.