You can try calling the venue, they'll know how long the show lasts.Has anyone been? We have tickets for myself, husband and 7 yo daughter who loves both artists. She has a long day of dance the next day and was wondering how long it would go?
Pretty much any concert I've been to is over around 11:00/11:30pm. Some go later depending on the number of encores, delays, etc.
A side note: DD14 and I saw Taylor Swift several years ago (maybe 5?). The concert was over around 1:30/2am or so due to a delayed start. The stadium had to be evacuated due to a severe storm (it was a football stadium - open air). She didn't go on until sometime around 11pm. We got home at 3:00am and had to get up at 6:00am for my DD10's horse show!