seesaw...its so cool that you are loving doing this stuff with the dogs.
If this were a situation with me...instead of Facebook...I would pick up the phone and talk to her and tell her exactly what you said here ...that her negative comments are counterproductive to all the work you are doing and you feel it is giving the dog less chance to find a good home because potential new owners will be Leary after seeing her negative comments...Confront her!