Yes, get her off those supplements ASAP, that is not good for her body or her mind. Remember that the examples we set as adults are carried through our child's lives forever. You don't want her to have food/diet issues later on too. You also really do not want to put her on a prescription that she doesn't need just so she'll lose weight, that is not okay. Start with the things that you can control, like what she's putting in her body and the exercise that she gets.
As another poster mention, start with getting healthy foods in and other stuff out. High Fructose Corn Syrup really is the devil! I too have read a lot about it and it is not good, those commercials are paid for by the corn growers assoc. after all! I think you need to be realistic, and it is hard to get rid of every single "junk" food thing in your house cold turkey, but giving fresh fruits and veggies and lunch meat without preservatives is a good and easy start. Also if you buy a lot of chips, think about getting pretzels or baked chips. Instead of ice cream, try frozen yogurt....just little changes could make a big difference. Read labels and buy fresh, the less ingrediets the better. Take your daughter shopping with you and let her pick out some things to eat or try, let her have a hand in the making of meals and snacks so she's more invested.
It might be fun to make a chart for her to reference as to what time meals and snacks are. It makes it easier for you to not have to answer all the time and she'll know when to expect it. You could also have her choose the menu (or at least part of it) the day before and you could do your schedule one day in advance so she always knows what's coming.
Lastly, I would make sure you're taking advantage of the cool summer weather and getting her to the park, the pool, riding bikes, playing games, etc. Exercise will not only help take the weight off but it will strengthen her heart and mind too!
Just a few suggestions, good luck!