I would teach her a "quiet" command. If she's sitting being good tell her quiet, yes, treat her (with food, praise, whatever she "works" for). Randomly do this throughout the day and then when she does bark tell her "quiet" and if she stops barking for a split second praise her.

Or you can put her on a leash and after a bark or two lead her away from the door until she calms down and then praise her.

Good luck. I understand how difficult it is...imagine having 5 dogs that feel the need to bark at everything