Hi Alex
You can eat whatever your friends of same age / size / appetite are eating. You don't have to eat the same amount of total food or carbohydrates within the meal each time. The only part that is different is that you and your Mum need to work out how much insulin to have with each meal, depending on carbohydrate content, blood glucose reading before meal, exercise you have done, exercise you plan to do after meal - which is what most people's pancreases do automatically.
Don't worry if sometimes you have blood glucose levels a bit higher or a bit lower than your targets occasionally - I still do after 12 years of needing insulin, and I didn't have the challenge of going through teenage growth aand hormone spurts, as I was 30 when I got Type 1 diabetes. But you'll cope, especially if you keep getting your Mum to type your questions here.