Letsmargaritatime sorry you and your DD are also going through this.
As a person who is very firmly in the "shift the focus away from the weight issue" camp, I am absolutely NOT saying let her eat whatever she wants! I don't think any child or adolescent should be allowed eat whatever they want. I absolutely agree that as adults it's our responsibility to fill the house with healthy food, leave out chopped fruit/veg for snacking, model healthy eating behaviour, and restrict pocket money if we know it's all going to be spent on sweets.
All of the above can be done without focusing on anyone's weight.
However, while all that limits the damage that can be done in the short term, it doesn't fix the core problem.
Focusing on a compulsive eater's weight makes the core problem worse.
Speaking as someone who had similar issues to the OP's DD, and overcame them, I stand by my original advice. A person with a healthy, happy, active, balanced life and a good relationship with their body tends not to mindlessly overeat. If OP can help her (obviously not very happy at the moment) DD to become happier in general, develop healthy habits, incorporate exercise into her daily routine, and build a better relationship with her own body (all easier said than done, I know) her DD will begin to treat her own body better.
The focus should be on staying active for tangible non-weight related goals, like achieving a certain number of steps a day.
Focusing on the weight creates a vicious cycle. The more you hate your body, the more hopeless you feel, the more you overeat.
I'm not saying it's simple - it's a long, hard battle. And I understand if you want to snap at me as I'm handing out advice when I don't have a DD with disordered eating habits - but the OP did come on here looking for advice, and I have BEEN a DD with disordered eating habits.
OP, that must make it very difficult that she is a picky eater. As Brandnewstart said she must be hungry if she is not eating healthy food and the hunger will make her more likely to binge.
Does she object to trying new food altogether?
If she's willing to try new food, it might be time to get creative with cooking. Roasted cauliflower, mashed sweet potato, spiralized courgette with pesto & sundried tomato & toasted pine nuts... There's so many different ways to get your veggies.
She has a sweet tooth obviously, so if you could get her snacking on grapes, strawberries, raspberries in front of the TV instead of chocolate that'd be great. I know she would never choose them over sweets - but if there's no sweets in the house and she's offered a big bowl of fresh grapes and strawberries, maybe she'd reluctantly take it, and that'd be the first step towards her getting used to snacking on something other than chocolate.
When I have a sweet craving I tend to go for a bowl of chopped banana and apple with natural yohgurt. It sounds pretty simplistic and maybe your DD wouldnt be a fan, but it gives me a sufficient sugar rush to keep me away from rushing to the shop for a Galaxy!
It's incredibly difficult to change your disordered relationship with food and your DD definitely has a struggle ahead of her but IT CAN BE DONE. It absolutely can be done. I was your DD once (except bulimic to boot) and now I work out regularly, I walk at least 5k every day, I'm totally cheerful about my thick thighs and belly squish, I have a great relationship with food and my body, I still allow myself treats but my diet mainly consists of fruit, vegetables and healthy grains. I haven't binged and purged in eight years.
Your DD can get there. It will just take time. I really really hope things start to improve for you both soon (and for your and your DD letsmargaritatime)