I have read the whole thread, and you are getting lots of great advice!
My DD was quite chubby as a young child, but she's slim now at 13. What I did notice from what you describe is that her diet is very carb heavy. My DD is quite the carb fiend, and I really have to work on balancing her intake, she would eat bread all day if she could.
So I suggest you look at healthy fats and good protein. The fats will satiate her so she won't crave the sugar and carbs as much.
Good fats and protein like eggs for breakfast (any way, boiled, fried, scrambled) as they will keep her full (she will need 2 or 3). If she likes it, she can also have 2-3 rashers of bacon or an avocado. Perhaps natural Greek yoghurt?
Nuts are great snacks, my DD likes pistachios and walnuts.
Does she have school lunches? See if you can avoid it because of the pudding. Give her a sandwich and cut up veg like carrots and peppers. Olives are a good lunch box addition too.
For dinners see if you can lower the carbs (ie the potato, rice, spaghetti etc) and give her filling veg like cabbage (I know, easier said than done, but thinly sliced cabbage fried gently in butter is lovely - most cooked veg are so much better with fats!) and focus on meats that she likes - my DD loves burgers, so I make cheese burgers with no buns and homemade oven chips. She also likes roast chicken and chili con carne with a small jacket potato.
For pudding you could see if she likes dark chocolate (in small quantities of course)?
I wouldn't worry too much about the exercise if it makes her angry. Just make sure you walk or cycle to and from school and avoid driving as much as possible - walk to the shops etc. Take what you can get, basically!