I'm so sorry you are going through this
Something is terribly wrong for a puppy her age to be acting this way, very over the top, even for adolescence. I would think more than likely it is physical, especially if it has been a new development and is quickly escalating. It may be some sort of hormonal or thyroid problem, as Top Barks said.
A vet exam for behaviour would include
complete bloodwork including
full thyroid panel (not just T3/T4)
Did the behaviourist offer anything besides a lack of understanding why?
Such as seeing you ASAP as you seem to need some intervention now, and any cases of aggression need to be seen by a qualified professional
Hope you can get to the bottom of this soon