AITA for skipping my cousin’s engagement party to hang out with my friends instead?

So, I F(18) recently got an invite to my cousin’s engagement party. It’s from my dad’s side of the family, and, to be honest, I’m really not close to them. I’ve always felt like an outsider when I’m around them. For years, they’ve belittled me and treated me like I wasn’t good enough. My cousin (the one getting engaged) has a younger brother who’s my age, and he’s ridiculously arrogant, always throwing insults my way. My other cousin (a few years younger than me) acts like she’s above everyone else, and I can’t stand being around her either.

To make matters worse, my uncle is unbearable, and my own dad tends to cause a scene every time we’re at a family gathering. At my uncles wedding a couple of years ago, my dad did his usual thing, and somehow, i got blamed and kicked out. I haven’t seen any of them since that happened.

This engagement party is right after my mock exams, and I really just want to spend the day hanging out with my friends. Some of my close friends from my old town, people I haven’t seen in forever, are going to be there, and honestly, I’ve been looking forward to it for ages.

On one hand, I feel like skipping this party wouldn’t be a big deal since I’m not that close to this side of the family and I’ve been treated like crap by most of them. But on the other hand, they are family, and there have been a few times where they’ve shown support. Plus, I’ll probably go to the actual wedding when it happens. But now I’m wondering if skipping the engagement party will make me the AH.

Would it be selfish to miss the engagement party to spend time with my friends, or is it fair given the history I have with them?