So you're really buying her a makeup set, dressed up as an Advent calendar. I think that sounds rather sweet, she'll have something to be a bit excited about every day in December.
As pps have said, it's your money, your choice. When it comes to feeling guilty, well, if the total cost of the makeup items would be about a quarter of what you'd paid for the calendar, I'd be questioning whether I was getting value for money, and thinking I should really buy the items and then make my own Advent calendar or equivalent. But if the markup is reasonable for what you're getting (I'd expect to pay more for them being packaged as an Advent calendar, just not several times more) then I can't see any need for guilt. Your dd doesn't sound like a spoilt brat in the least, and £60 on makeup for a teenage girl isn't completely out of the ball park if you have the cash.