How to lose a potbelly PRONTO?!?

Okay, so I'm a 12 year old girl, the last time I was at the doc I was "4'11" but I measured myself and I think that I grew an inch... I measure 33-29-35 (or 36) and I have a GIGANTIC, 33 INCH WAIST (belly on). Which is ironic because my friends chests are twice my size, yet their waists HALF my size and they eat junk like pizza, cookies, and ice cream while I haven't had anything like that in years. MY idea of bingeing is eating a skinny cow low-fat ice cream bar. I like my legs and arms but I HATE my potbelly, muffin top and love handles! My mother said my older siblings (who are VERY lean) were the same way when they were my age but I don't believe her because I have seen pictures and they still looked very skinny. I have seen mothers in their 40's who had better bodies than me. Please help me. I'd like to AT LEAST get my waist (belly on measurement) down to 25 inches, if not less. My mother does not support weight loss so don't recommend any crazy weight loss supplements.