She must be really stable not to bark yet. I think it is a good sign. The best protectors are the ones who are not afraid of strangers. The barkers will probably hide behind you or snap out of fear. I think when she matures she will start warning you.
WD never barked at strangers either at that age. But when one of our nephews ran up to me WD immediately positioned himself between the boy and me. I was pleasantly surprised.
Deja, GSD, sable WL, female, born 11 / 2013
Cam, Rough Collie, sable, male, born 8/2015