Have you thought about letting her have control of her "sweet" and general food intake? I know it sounds counter intuitive and most people say "but he/she will just only eat crap!!!", but HONESTLY, it works.
We practice self-directed eating with DS and I have a few RL friends who do it with their kids.
In follows on directly from BLW - you make foods available, either through mealtimes, or simply having them in the house, and the child directs what they eat. We have meals together as a family but if DS doesn't like it, he gets something else for himself. DS is 7. He chooses sandwiches, soup, yoghurt, fruit, cheese, left overs, whatever he can find in the fridge. He has a sweet tooth like most kids, but does not eat any more than a typical child, in fact probably less.
DS is involved in choosing meals, shopping and preparing meals (when he can be bothered!)
The only time he is EVER coerced into eating is at school by the dinner ladies! I should add that he has Asperger's and can be VERY faddy about his eating, but because he's self-directed, it's his business. I keep a general overview and sometimes make educated suggestions to him about foods (because adults about things like fibre and such), but food is a total non- issue for us, other than really enjoying ourselves.
If you introduce it to an older child, rather than following on from BLW, they do go through about a 6 week phase of gorging on forbidden stuff, but it soon passes when they realise that these previously regulated foods are available and will not be limited, or taken away.
Long term, it helps develop a much healthier attitude to ALL foods, as the child learns to listen to their body and eat what they want/need.
We also do not refer to ANY food as treats. It is all simply FOOD. All valid choices and delicious, enjoyable and valuable.
If you want to know more there is a fabulous book called Preventing Childhood Eating Problems by Jane Hirschmann and Lela Zaphiropoulos. They have worked with people with eating disorders and the book was developed from their research.
Jane Hirschmann also has a website called Overcoming Overeating:
overcomingovereating.com/