Both Kaija are the real Kaija, also there is another path which she is not lying bitch. In there, she is unsure about her feelings but loyal to the Templars without question. All 3 stands there as alternate reality of Kaija.
To sum them up,
in her cheating, lying bitch path. Everything she does, she does that because it was her duty. She openly admits she acted as as MC's lover because it was easier that way. Also admits everything was a lie. She also kinda mentioned how big of whore herself to sell her body, her mind, her soul to the Templars, between the lines. She is basically a religious fanatic, a devotee and her religion is the Templars. I speculate in this path, if fake Jason Statham orders her to kill MC her only struggle would be choosing the weapon. In this soulless bitch path, she sometimes claimed she thinks MC as a friend but snakes cannot trusted, so I don't think that is true. Also there are some strong indication, their friendship was deteriorating when they were growing up, so even their friendship can be faked by her and maybe even now, she is trying to manipulate MC to look like his friend, to use him further. All in all, all she deserve in this path is a blunt stake through her and some oil to burn.
In her unsure path, she still follows the Templars. She executes orders without question but she has some feelings towards MC. She feels more than friend, that much is clear. I should admit, I think this path is her the most human path also most natural. What I see in this path, a woman who robbed her childhood, her life by some cult. If she was given choices she may love, live a good life but instead she raised as an assassin to do their deed. She is not sure what she is doing, what she is feeling and I believe it's because she does not have any reference point to be sure, her only life is given to her by other people. I kinda pity her in this path and I am most sympathetic towards her.
In her love path, it starts as her whoring herself for Templars' interests path. She is friends with MC, she recruited by Templars. We don't know much about how but if I have to speculate, Linnae told MC most recruit is from families and Kaija's family is a mystery so I think her family, grandfather iirc, is a Templar and she became a Templar through that. Maybe she is even groomed to a Templar and friend to MC by Templars. There are some indications towards that but nothing revealed yet. Anyway, after she became a Templar she ordered to protect MC. First they tried to force her to be a lover to MC, that is prevented by MC's father, grandmaster of Templars. In the beginning, like Salem path she was only a friend to MC, then she started to develop some feelings towards MC. When everything reveal at the MC's parent's house she was in love with MC. My problem with this path, she claims to love MC but Templars still is more important to her. She robs MC from everything with MC's parents and she justifies that because she believes her order is bona fide. Most of the discussion is about Kaija's this path because people who defends Kaija either don't know the other path or have some decency to not defend her witch path.