Get him.

Hi all. Ever since we were robbed Shadow nearly (1yr) has become extra vigilant in investigating new noises around our house.
She has also shown us a new trick/command that no one here taught her, but now my older son encourages. Shadow seams very happy showing off her new trick. My older son say's "get him" and raises his arm, Shadow will jump up and bite his arm, she will hang on until she is given the release command. My son was showing his friend all Shadows tricks (friend was suitably impressed) Son says to Shadow "get him" but was inadvertently pointing at friend, Shadow started to leap towards friend, son says"leave it" Shadow stops in her tracks.

I must add, Shadow is well known around here for being tolerant, friendly etc. She has never shown any form of aggression. Is this new trick something we should be worried that she will show off without the "get him" command in a situation where she has no need to be protective? I also need to add nothing else about her personality has changed, she is still placid, just more alert. She doesn't seam nervous when alert, hyped, perhaps.

I'm waffling now, oops thanks.