It is not extra effort, just make the same food and substitute the meat with vegan quorn.
And plant milk, that goes off before the one person drinking it finishes the carton, and that has to be bought from the supermarket not the milkman.
And vegan cheese which is disgusting and nobody else will eat the dish made with it. BTDT.
And getting exactly the right kind of biscuits and your family eating the ones that you bought specially GRR.
And about 3 things you can put on your sandwiches, two of which involve going to a special shop - bet the 10 year old isn't doing the shopping.
And buying egg substitutes if you want to bake which ditto come from a special shop.
And vegan mayo that nobody else will eat so goes off.
I have been that one vegan in the family and I'm the cook. And an adult.
If she's old enough to cook for herself and meal plan that is a different matter. I'm old enough to cook for myself and meal plan. I still found it a pain, and more expensive, and stuff went off before I could finish it because I was the only person eating it.
Honestly, these days, being vegetarian is not any hassle at all. That really does involve just substituting the meat, and a 10 year old will get all the nutrition she needs. But being vegan if the rest of the family isn't is still a huge pain.
I really don't see why the OP (and it will be the OP, not her DD or her DH) should have to do loads of extra shopping, planning and cooking.