Refusing Cousin’s “Dibs” Concert Ticket

AITAH for refusing to give my cousin my concert ticket after she “called dibs”?

Okay, Reddit, I honestly don’t know if I messed up here,

so I need outside opinions. I (16F) saved up my own money for months to buy a

concert ticket for my favorite artist. I bought it the second tickets dropped, and I was SO excited

because it sold out almost immediately. A few days later, my cousin (17F) found out I was

going and got upset. She said she “called dibs” on going to that concert months ago when the artist

announced the tour. The thing is… she never bought a ticket. She also never asked me to go with her

or to buy one for her. She then told our family that I was being selfish for