Would you allow two teens to go to a concert by themselves?

She’s turning 15f and wants to go to a concert with her friend (also 15f) for her birthday. Tickets are reasonable but it is an open air venue (lawn seats) and there wouldn’t be a chaperone going either. She doesn’t have any plans the next day but it’s a weekday. We have work the next day and can’t stay out until midnight for a concert.

They may have a ride back with a different parent but my husband (his daughter, my step daughter) isn’t very comfortable with them going without a chaperone. He asked my thoughts and I’m not completely comfortable with it either but she is getting older.