At six months old, your pup is probably not really showing signs of aggression, she is testing the waters, to determine what is acceptable and what is not acceptable. It also sounds like she is slowly becoming over protective of you. You are very perceptive to notice such subtle changes.
Gentle scold her for growling. You might even try "time-out" for brief periods (5 minutes) in a crate that is isolated. Good luck and just keep on keeping on. Sounds like your baby is blessed with a wise, kind, Mom!
