Ok to be hurt???

I just want to know if I’m being a baby about this.

Tomorrow my husband and I are taking my 18 year old sister to a Post Malone concert. I’ve wanted to do this for her for a long time now. I have spent a lot of money on this. Our tickets alone were $330+. Then we have the gas, hotel room, food, souvenirs. I was really excited to have just me and my sister time. My husband is only coming along because I am scared to drive in the city. Well, she just informed me that her boyfriend that I haven’t even met yet and all of his friends are going to be there too and will be coming to sit next us. The theater we are at is a big outdoor one, no assigned seats. I mean, I know she’ll have more fun with them because they are her age and love Post as much as she does, but I’m just sad that our sister time will be ruined now.....