Maybe you could get her involved in planning the food and shopping? Rather than discussing it as an emotional or weight issue, look at it as a health thing. Talk about the fact she's getting older, her body will be changing and she'll need different things from food, and where to get these (stuff like protein and sources of it, that the different colours of veg have different nutrients, healthy fats etc), and that for a balanced diet and proper growth, particularly through puberty, she needs all of these things.
Look at possible meals online, maybe on things like gousto or hello fresh, and then plan a menu for the week, including snacks and treats. Snacks should include healthy fats and protein to keep her full for longer (so adding cheese to crackers for example, or putting peanut butter and banana onto toast).
To be honest, filling up on carbs doesn't sound like that terrible of a diet, but if it's a genuine problem, then consider this when plating up meals - carbs should make up about 1/4 of your plate, with protein 1/4, 1/2 being fruit and veggie, and also include some healthy fats. Try to stick with this, so if having spagetti for example, pack out the sauce with veg like peppers, onions, carrots, lentils, celery etc, serve with some salad on the side, and reduce the amount of pasta on the plate. Don't make it a temporary diet, but a conscious change to what you eat to include more fruit and veg.