AITAH for skipping my cousin’s wedding after she excluded my sister from hers?

I (24 F) am considering skipping my cousin’s wedding reception and now I’m wondering if I’m being petty.

For some background, my cousin and I grew up fairly close. There’s no bad blood between our families at all. My parents, my siblings, and I have always had a good relationship with her. When my older sister got married, my cousin was invited with open arms. Hell, we even get her a room at a freaking 5 stars hotel—breakfast included.

A few months ago, my cousin (somewhere mid 40s F) had a wedding ceremony in another city that’s very far from where I live. Interestingly, my sister actually lives in that city. However, my cousin chose not to invite my sister because, according to her, that event was “just for friends.”

The thing is, the event apparently had dozens of guests, including influencers and celebrities, since my cousin and her husband are in a very different financial and social circle than the rest of us. Several of our relatives even encouraged her to invite my sister since she literally lived nearby, but she refused and insisted that my sister was only invited to the later family celebration.

Unfortunately, my sister couldn’t attend the family celebration because flights became almost three times more expensive by that point. So despite being immediate family, she effectively ended up excluded from both events.

What bothers me is that my cousin invited her younger sibling and niece/nephew to the destination wedding, but not my sister. My sister had done absolutely nothing wrong, and there has never been any conflict between our families.

Now the family reception is coming up. The event starts at 4 PM on a Thursday, which is exactly when I finish work. The wedding is in another city and requires about 2.5 hours of travel by train. Technically I could take time off, but getting leave approved at my job is difficult and I would have to use one of my limited vacation days. Before everything that happened with my sister, I probably would have tried harder to make it work. But after seeing how my sister was treated, I honestly lost a lot of respect for my cousin. I understand that brides and grooms can invite whoever they want, and I fully respect that. But at the same time, I feel resentful about being expected to make sacrifices to attend when she couldn’t extend the same consideration to my own sister.

Part of me feels guilty because we used to be very close, and there’s no open hostility between us. Another part of me feels that I shouldn’t have to use my limited leave and spend hours traveling for someone who excluded my sister when she easily could have included her. I always love weddings so there is a little FOMO in me, but the weight of it all makes me pissed.

So, AITA if I skip the wedding?