Pizza has double calories compared to rice.
a 100gr of rice only 130kcal while pizza is 260. Don't mention chips.
Maybe your mom overreacts (bones will come out and die), but it's better to eat rice than pizza or chip (junks). While the 2 are refined carbs, rice is still healthier. Or if you're concerned w/ health problem you can try brown rice. And try to negotiate w/ your mom and make a win-win solution which you two can accept.
Be grateful when you still have a mom, I wish I have my mom to scold me again.