i would get her fasting blood sugar checked immediately for the possibility of type 2 diabetes.  At this age there are a number of great options to halt the weight gain and get her more physically active.  You probably need a full medical evaluation and i would get the whole family on baord for a 'family ifestyle makeover' since these habit shifts are difficult when you isolate the child.  My book Fat Families Thin Families focuses on helping the whole family shift habits and adopt better eating and exercising habits - for the sake of the children.  these kind of lifestyle changes require the support of a doctor while the family works together on meal planning, snack planning, acitivity planning and targeting specific personal goals.