That's an interesting take on it. I had mostly just seen her as "the annoying one". With the risk of sounding disrespectful of Moonbox I think there might not be that much thought behind it, the rest of the game has been (as far as I recall) rather light on that kind of psychological depth. But I could be wrong about that. And with that said, my favorite part of this game is the story. I actually usually click through the sex scenes rather quickly. So I've really enjoyed these latest story-heavy updates.
You're not wrong, the majority of the characters have been pretty shallow, with the notable exception of Aunt Amy and her backstory.
It's possible, hell maybe even likely, that I'm seeing depth to her character where none is intended, but at the same time, I'm only going off what is actually written and shown.
Like all we ever got before of Annabelle was seeing the spoiled tyrant, and coupled with what Ophelia said about not being good at disciplining her when she was growing up, we're lead to believe that's all there is to the story.
But it looks like Ophelia never actually showed Annabelle any love or affection when she was growing up either. I wouldn't be surprised to learn Annabelle was largely looked after by Ophelia's staff. The staff likely weren't be paid to raise her, simply to mind her, so no love or affection from them especially depending on how young she started to grow into a tyrant.
I'm thinking that Ophelia was much more present and hands on with the raising of Sophia, than she was with Annabelle given how drastically different they both are in their base states, and how little Sophia is shown to actually care about her mother.
Annabelle is only now, it seems, learning what affection is on a personal level, and that kindness is often returned with kindness. Like so much about her character makes sense if you think of her as being like a rescue animal was constantly neglected and abused by their previous owner, and now their new owner need to take time to rehabilitate them with patience and love.
Of course the real tragedy here is that none of this matters and MC will most likely continue to treat the same as he ever has and continue the borderline abusive BDSM with her rather than adapting to (what I at least see as) new information and circumstances