Just to confuse the issue, lol, IF she has consistently been a good kid I'd rethink the situation. The face that she asked permission months in advance makes me assume she does not have a history of defiance. Only you, of course, know how the first sixteen years have gone.
Although I don't know your family I have raised eight teens and "revisiting" choices with them strengthened our reltionship. So....I'd consider taking her somewhere like Dairy Queen (change of venue from the familiar helps) and then tell her that you've been thinking about the concert and understand it is important to her. Tell her it is 100% normal for Moms to worry about awful things that "could" or "sometimes do" happen to lovely young innocent girls.
Ask her to consider a compromise that you both can accept.
Maybe she and her friend could "live with" being driven to the location so long as you don't insist on dropping them at the gate. Maybe she would agree to text or call you for pick up when the concert is over. (This worked for me with both the teen girls and the teen boys so long as nobody saw me, lol.) You can make a good case for her not taking the car alone. Most importantly you want to convey that you understand her position and you are not trying to have a power war. This first "battle" choice may determine how the next few years go. I wish you luck. DDD