A lot of people think they are feeding their child healthy well balanced meals, but when it comes down to it what you put into your body (or your child's) may not be as healthy as you think.
I went to a nutritionist to help get me started losing weight and some of the foods I thought were "healthy" turned out to be just as bad as junk food. Potatoes, corn, and other starchy veggies are not good for you, they raise sugar levels and make your body store fat. Unfortunately corn and potatoes were major veggie staples in our house, we ate one or the other every week sometimes we had both in the same meal. So now I limit it to either corn or potatoes once a week at most.
If you give her juice, make sure it is no sugar added and keep to the serving size indicated on the box. If you give her whole milk you can switch to 2% to lower the fat intake she gets from the milk. I am blessed with kids who LOVE vegetables, so I give mine raw broccoli, colliflower, carrots, and leafy green salads as side dishes.
Sugary cereals were a culprit in our house too. I still let them have it but only a couple time a week and only when they ask. They get breakfast at daycare so I normally don't have to worry with breakfast except on weekends.
Talk to a nutritionist. We have one at the hospital that is free as well as where I work (at a university) but you can probably even correspond with one of them by email if there is not one near you. Just Private message me and I'll give you an email address for them.
I learned so much from the nutritionist and my kids do not have weight issues, but since my state has the largest childhood obesity rate, and since being pregnant with the twins I gained 80 pounds and am having trouble losing the weight (I still have 50 pounds to lose for my pre baby weight). I wanted to start making better choices for them and fostering good eating habits.
I am not saying I never let my kids have soda, or junk food, or ice cream, just not everyday and not in excess. They don't seem to mind too much, they don't really know the difference.