What is wrong with my dog? (psychological question maybe?)?

Since she had a previous home, and you have no other explanation, it could be anything. I would go as far as to propose a scenario in where there was an abusive male in her house towards a female human and her. Maybe when all three of you are together it just looks too much like what it used to be for her. Just a suggestion. But I have to say, I think it had something to do with her previous home.