Should I be comfortable with my boyfriend going to a concert with another girl?

amIcrazy
My boyfriend and I have been together for a year and four months now. We have been basically living together for about 8 months. Lately he has had this friend who is a girl pop up out of no where. He is really social and has a lot of friends but she's not someone he's mentioned to me before. A few weeks ago she asked him to pick her up from the airport. Now he is going to an out of town concert just the two of them. He did ask me if it would be okay if he went. My immediate reaction was "yes, go, I don't wan to sound like I don't trust you." They are coming back tonight. I tried to talk to him about how uncomfortable I am with it and his response was that I am being jealous and I don't trust him, just like I had thought it would be. I also mentioned that I would feel more comfortable if I had met her and he told me he has a lot of friends that are girls he might want to go hang out with without me and doesn't feel like it's necessary that I meet them. Should this bother me?
Should I be comfortable with my boyfriend going to a concert with another girl?
4 Opinion