You can do this.
Take away is awful for calories and massive portions but it's easy done so when it does happen try and be the one that orders, no need for naan bread, get boiled rice to share instead of fried. Tomatoes based sauce instead of cream but just avoid all of you can
Make dinners super healthy and filling stop buying good snacks that's easy to grab calories, veggie sticks in the fridge that are easy to grab or cooked meat/seafood sticks if she really can't wait till dinner
No one needs to snack after dinner before bed
Try and walk with her as much as possible and encourage school dinners instead of packed lunches, it's so hard to fill a healthy yummy packed lunch for a kid without it being so obvious what you've done taking away the cheese, chocolate and crisps
Weighing out cereal to see what a child's portion really looks like and do some sums to see how much she really pours it'll probably be two days worth of sugar (I've done this before with kids) it's always a shocker
I put on weight at the same age, my mum was so conscious of it and made dinners too healthy and bland and I was always starving and never had anything "good" to eat in so as soon as I got cash I would hit the bakers and fill up on tummy things. Then I would go to my dads and binge so be careful how you broach it
Fitbit at Christmas is a great gift though if you both have them and get a bit competitive