Grace is pretty tall, she can carry more weight for a healthy BMI.
There was a tv show a while back, something liked "secrets of the superkinny", and it did tests that showed a lot of thinner people do incidental movement and burn ALOT of calories throughout the day-fidgeting, cleaning, gardening. She quite often says she goes on walks with friends and always seems to be on the move.
There's this thing called your basal metabolic rate, which takes in to account your height, gender and age (she's tall and young) and this is the number of calories your body needs to just exist. There's also TDEE, which is Total Daily Energy Expenditure. If you're moving around a lot, or even just standing up a lot (like standing in a kitchen baking), your expenditure is greater.
She seems to eat a lot of snacks and sweets, but her meals don't seem that big. Andsome of her snacks arelow calorie- quavers, popcorn.
I think it looks more than it is because she showed a whole packet of bagels, two different jars of chocolate spread, several boxes of biscuits and packets of cookie dough, a load of cookies she made for her tiktok, a whole load of donuts, dinner for her whole family, a big bar of chocolate,big bowl of popcorn