haha poor thing, next time ask some questions first

You were her back up, in case her boyfriend bailed... FYL OP

I don't care what anybody says, OP paid $60 to watch the girl he likes make out with her boyfriend. No amount of "glass half full, on the bright side" optimistic advice is going to change that. OP could have been a little more diligent with regards to her relationship status, because generally if you're feeling someone, you ask around or ask directly whether or not they're seeing someone. OP having to pay for the ticket though? That was a dick move.

If you invite someone to an event saying that you have an extra ticket, it's usually implied that the ticket was for whoever is being invited. If not, she should have clarified. Idk why people are telling OP he shouldn't have assumed it was for him

Need a fedora?

I wouldn't have gone in then

If you know her well enough for her to invite you to hang out at a concert, then how could you not know she had a boyfriend? Your friendship (and therefore your crush on her,) must not be very deep or genuine. You'll get over it in time.

Did they ask you to drive?

Was it at least some good music? if so i wouldn't be mad at all, if it was some shit i really didn't like i would have just left honestly.

I've had the same experience dude