My daughter attends cadets two nights a week from 7-9pm. It's about a 30 minute walk and she doesn't mind walking, however, I have always picked her up at 9 because I feel like it's a bit too late for her to be walking alone. DH thinks that when it's light she will be fine walking home, I just feel like 9-9.30 is too late for her regardless of how light it is.
YABU - she will be fine walking home
YANBU - it's too late for a 12 year old