Then, when you're 25, your daddy dies aged only 56 and after a rather brief period of mourning you get pushed into taking his job in a pompous ceremony. Now you're going to be doing this until you die. No retirement! I bet there were times where Lilibet just wanted to go to her room and cry.
I wouldn't have wanted her job for all the wealth and power that came with it.
[1] Well, you could make a big scandal about marrying an American divorcee, but that didn't go down too well for the last guy.
She did go beyond simply maintaining the monarchy - she worked to influence legislation to, among other things, hide her personal wealth, give her and her family an exemption from seatbelt laws, and make it easier to lease land for development. Pretty minor issues all things considered, probably much more mild than the average MP, but it does not sit right with me given that she was unelected and in office for life.