Change the snacks to fruits and veggies
Stop buying snacks simple
Don’t do anything. Let peer pressure do it’s job
Keep active. Less sugar.
Follow Kids Eat in Color honestly great advice
You worrying about her weight before she’s even hit puberty, is a sure fucking way for her to become self conscience. 
Maybe, just maybe, don’t fucking worry about her weight unless her doctor has. If she’s not lazy and eats fine then she is NOT FUCKING OVERWEIGHT!!! She may have a thyroid problem or some other underlying health condition but you wanna put an EIGHT YEAR OLD on a diet???
Some people shouldn’t have kids.
Does she buy the groceries cause that odd
Outside Activities, team sport like Soccer, tennis
Only buy healthy choices and stop letting your kid eat an drink junk an sugar.
Don’t buy junk. Period.