At what age can people go to concerts?

My 10 year old sister wants to go to a Nicki Minaj and Britney Spears concert with my mom of course, while I stay at home with my grandpa. She's so interested in music (Lil Wayne, Rihanna, Lady Gaga, etc.), I think she's too young, isn't she? So, at what age is it possible to go to a concert? Thanks... best answer is told to my sister lol xD