i don't think they gave her 2 month of therapy and she was cured. they only took 2 months to convince her that they have a reason to use her as a chess piece and she fitted the role. since she has been a smart ass, reading and disagreeing with her farther and all, she caught on it.
is she broken? sure. she closed up and ignored the outside as somewhat defensive measure, but she did not show signs of being mentally impaired or suffering from high actives response disorders (like panic attacks). she could hold in and accept so much abuse and the way she reacted in the beginning was the way she thought would be needed to stay alive.
keep in mind that it is five years of trauma but she gave up everything, so with that her rational was preserved. unfortunately, it means she is a somewhat empty and nihilistic puppet who works in the premise she would do anything as long as she stays alive (her biggest mental scar should be being almost zombie like and robotic). that is her foundation, staying alive. she looks like the kind of person that wouldn't mind losing an arm to stay alive or make use of her body (prostitution).
is she implausible? completely no. humans are very adaptable and that is somewhat a very dark characteristic of ours. if she was very attached to her life as a lady or the past, sure how fast she turned wouldn't be plausible, but to someone who gave up everything or had very little from the beginning, her recovery to such a point isn't a miracle. it is survival. some people clutch at every opportunity they get, and those are generally the ones who go through the worst kind of shit (once you lose most hope, being miserable and still struggling seems like a fine choice).
if she was someone with a 'giving up' personality, she would have killed herself long ago, in those five years of terror (i am sure they gave her the opportunity -_-). she is a survivor tho. in addition to that, she is smart, very curious and takes the initiative to learn.
now, if tomorrow she falls in love with that guy, go bonkers. makes no sense. also, if she decides to give her life for her master out of her heart... nope, no sense.
also, note that because she lost everything it doesn't mean she can't appreciate the nice things... those who really suffer the most are the ones who appreciate your 'burnt bread'.
you can still see the scars tho. her perfectionism. her unemotional response. her semi robotic logic. her coldness. her straight forward line of thinking. her fear towards people.
she is broken, but she has been surviving such long ago.