What makes you think she's over weight? Does she eat unhealthy foods? Does she move a lot, like most children do, perhaps do some sort of organised activities, like soccer or dancing or something like that?

FWIW, I think eating healthy, whole foods and being active would absolutely be enough. There should be no reason that she should be over weight if she's doing those things. But we also need to remember that everyone is built differently, even our kids. She may tend toward being bigger in size. Maybe she's just growing faster than her peers, and will slow down later. Maybe her hormones are starting to rage. Maybe her body is hanging onto fat for a big growth spurt. Try not to project your own worries and childhood memories/experiences onto her. If you feed her health foods, give her opportunities to be active, and teach her good habits, she will grow to be a normal, healthy person.

Though, if you're still concerned, maybe a trip to a trusted and well educated doctor/paed (ie, not one who relies on stupid growth charts/BMI charts) would ease your mind.