Can you tell other people kids to stop doing something they shouldn't be doing?

i think she did the right thing. the kid at 10 is old enough to know right from wrong. he could have blinded the tiger, better to tell the boy off and stop the animal being hurt unnecessarily, if ur gf had said nothing it would not have helped the tiger any and there was no harm done to the boy, infact the boy probably prefered it that way, if his parents had found out he might be in all sorts of trouble (since if i found one of my kids doing that...hypothetically since my sons only 11 months old so not old enough to do that kinda behaviour yet..... then i would have them grounded faster than u could say boo.... no gadgets to play with in their rooms and only allowed to watch animal conservation programs on tv until they were ungrounded! tut tut!