It’s pretty fair to treat others and give them the same consideration that they have given you, when it comes to being thoughtful and celebrating important milestones and events, you can’t expect someone to celebrate things for you that you ignored for them.
Still, there are things that are different between the expectations in the behavior of a child and a grown adult and picking a fight with your 13-year-old nephew about his birthday. Kids generally aren’t very good about remembering and celebrating the birthdays and events of their own parents without being expressly reminded, and I don’t think I’ve ever really got my aunts and uncles’ birthday presents out of the blue.
We had teachers in school who liked to pretend that they were one of the kids and pick fights with the students in a vain effort to relive their glory days, and even as a teen, it was easy to see how immature and inappropriate that was. We expect different things from teens than we do from adults; something to do with a fully formed brain and frontal cortex should result in better and more mature behavior.
This could have been a good life lesson for the kid if delivered in a measured way but delivered in the way and with the intentionality that this was it just makes the aunt seem really immature and guilty of all of the things she has accused her nephew of being.