Personally, I think she is a love interest. Their break-up was due to the trauma from [BACKSTORY], not some mutual resentment or anything like that. As I see it, the reason Sonya doesn't have a Love/Lust score is because is would be completely redundant. They both still love each other, so there's no point in counting the points because she would basically start out capped. I think she'll be an option at the end, either for players who didn't commit to anyone, or just always there anyway, EXCEPT!
EXCEPT for high-Depravity runs. I only tried a Depravity run once so my memory might be a little fuzzy, but she does not appreciate the few moments where you have the chance to go all mega-prick on her, which really makes me think at the end of a Depravity run she'll just hate the asshole you've become and leave you to your misery.
It makes me wonder, towards the end of the game, if she is going to get in-between the MC and whatever girl he's fallen for, in my case, Katie.
Charlie/Tex/Brokeback already told her and she doesn't give a shit, but maybe deep down, she still might...? The MC already stopped Henry from killing her. Katie, before you pick on who you go to the Pit with, was like "Oh yeah..." after Ellen said "why is your bitch wife here." I think picking her for the Pit mission will remind her how much she still loves him because it'll feel like old times and they'll bond again.
If this game's ending is anything like DA, the MC is going to get severely fucked up before it's all over. I know you could die in DA, but I'm wondering what's going to happen here, especially since, well in my case, both Katie and Sonja love the MC. You can tell with a high score with Ellen that she really does care too, because of their past.
There's going to be a lot of things to iron out between Chapter 10 and the finale in Chapter 14. I think Katie can handle Sonja in an argument.
