You must be running a fever if you (mostly) agree with me.
Of your comment highlighted in red, talk is cheap. I'm a realist in that when two people have been in a long term relationship, they can talk all they want to a therapist but to actually change behavior,....that's not going to happen (been there, done that). Nina being a narcissist (or Kira being subservient) doesn't happen overnight. These are behavioral traits that originate from family upbringing. If someone truly wants to change, it will take years to be constant and show growth with that change. It might be easier for an alcoholic to go dry then a narcissist to be aware of other people's needs. Some people are not meant to be together long term.
*I* think once anyone is out of the house and have developed habits, they will not change. Better to find someone with compatible behavior traits (that compliment yours) than try and fix something that has a 0.01% chance of working.