Too skinny to be on a diet?

my mother wants to go on a diet and i'm encouraging her because it will be good for her weight/health. Then again, she is buying food that wont make it tempting for her to eat. my point is... all the food she buys at the market is food that will help you lose weight and i'm stuck with only that too eat. i'm 14 and only 95 pounds im sure a diet is the last thing i would need. when i ask her for a bag of doritos or something she says "No, im trying to watch my weight" i guess she doesn't understand that im not. How can i get her to buy things we both can eat that wont affect her diet?