well it could be interpreted that it looks at what your active's current trait is (not necessarily decision)
since you probably didnt have altruistic or egotistical at that stage since its like early in the game, then it just chose randomly
but now that you gained the egotistical, next time he will go for altruistic
Mmh, didn't think about that, might be actually the case.
I keep an eye open for further decisions.
@Larzare, have you tried reloading to see if the AI selects another answer when you switched yours as well?
Nope, I was quite happy when she (my 2nd character) decided with me

I also don't have that particular save anymore.
If the "free" personality actually turns out to be opposite of your active character that would be silly. Free has a totally different meaning, at least for me and I might restart/change personality. According to the chart on on the website posted somewhere above Priest or Spiritual might be fitting more with what I had in mind for my 2nd character.
Edit: it would be awesome to have a little character summary when selecting an AI personality. Hope they add something like that in a future update.