Agreed.
This chick is a cunt. Plain and simple. People make mistakes, sure, but this isn’t a case of making a mistake. She did something she knew would hurt your feelings and make you angry, and took something away from you that she knew was important to you and gave it to her friend who just wants drugs.
People who go to shows just to score drugs are the scum of the fucking Earth and shouldn’t be allowed to go to shows. They’re part of the problem.
Unless it turns out that this was all some elaborate way of letting you meet the band or giving you a sweet gift, you need to seriously think about this relationship. It’s easy to lie to yourself about someone when they mean so much to you, but ‘Cate’ has made it clear she doesn’t really give two shits about you.