the key I find for a dog like this, is to have EVERYONE put her on IGNORE. No eye staring, no touching, no treating from strangers NOTHING..She does NOT exist to strangers (or people she tends to bark at)
If you want to work with someone, figure out what her comfort zone is..that is the zone where she does NOT react. So get a friend who's willing to help out..approach, as soon as the dog reacts, turn around and back up to the point where there is NO reaction..Walk in circles, go thru your obed commands, reward for being quiet..keep her moving in her comfort zone.
(I would have the person helping you to stand in one spot and not move at the beginning of this and NO staring or watching the dog, tell them to ignore her, give them a newspaper to read
Also have on hand HIGH VALUE treats (hotdogs, chicken whatever, used ONLY during these times and for good behavior)...
You want to start closing that "zone",,it could take doing this daily for short intervals, and I would say best with no other distractions.
As you close the "zone", and keep rewarding for good behavior,,hopefully you get to a point where you can stop, have her sit/.down/stand whatever, and start carrying on a conversation with your "helper"...If she shows interest in the person, FINE,,as long as she is quiet, your "helper" has her still on IGNORE...Have him toss random treats, (the high value stuff),,still ignoring..let her call the shots..
IF she's a food hog, she's going to start seeing those "strangers hands" as a FOOD dispenser..
I wouldn't push strangers on her or allow them to pet her, stare at her, she's obviously reacting out of fear/i'm gonna get you and if I bark enough you'll back off..
Using a clicker to mark her good behaviors is also a big plus..you click, you reward, she learns to associate the click with YOU getting a good behavior from her and SHE gets rewarded for it..
Just some ideas