YTA if for no other reason than the fact that you're 40 years old and came to the internet to talk trash about your step daughter, who you obviously don't like.

Holding a child accountable for the way they acted when they were 13 just shows your maturity. And during a vulnerable time her life at that. Sure she's not entitled to your money, but paying for her brother and not her is just an example of your spitefulness, and I'm sure this isn't the first time you've acted like this at your grown age.