Am I just overreacting?

So my friend and I bought tickets to go to a concert together. I ended up having to move 3 hours a way like a month before the concert so we both mutually decided to sell our tickets. Well yesterday I was browsing snapchat and she was posting pictures going to the concert with her other friend. I don't care that she went, I'm glad she did. But I feel as if she should have told me she was using my ticket and because we agreed to sell them I feel like her friend should pay me seeing as we were selling them for the price we paid which was over a hundred bucks! So I basically paid for her friend to go. I'm really hurt and honestly can't believe she would do that. And now she won't even talk to me. Am I overreacting?