My take on this would be to keep on manipulating the aunt into sex with the help of the bible and its interpretations.
For example:
Then create a situation where the sexual acts appear more coerced, with Charlotte being torn between the triangle of
< must help him and obey >< must stay true to my old celibate identity >< actually learn to embrace sex / sexual submission >
So her growing doubts make her initially insecure about repulsing advances, then she pretends to not enjoy it, though eventually ends up depraved where she even secretly enjoys anal (which is still explicitly condemned for all abrahamic believers)
Most of this is pretty close to what I have in mind.
Charlotte is coded as some kind of weird Pentecostal variant where the emphasis is on biblical literalism (although typically selectively applied), personal relationship with jesus, spiritual gifts (prophecy, visions, casting out "demons" etc). Celibacy is not typically a feature of Pentecostalism, but you could very easily justify it if you emphasize Paul's letters and throw out the entire Old Testament, which many Protestants do, except when they want to shit on certain lifestyles that aren't to their liking.
I get what you're saying. The things you list could be use as arguments against her to give a rationalization or sow the seeds of doubt in her and give a rationalization for why she ultimately "partakes of the forbidden fruit." I didn't think of the Adam and Eve angle, but I did think of Lot and his daughters.
Since the game is set in the 80s it might be in setting to utilize the satanic panic hysteria as part of the story telling and plot. I'm just not sure how into the weeds that would take take this porn game
This is touched on a little bit in two scenes: the scene where Charlotte plays Brooke's records backwards looking for backwards satanic messages, and in the scene where Charlotte is found snooping in MC's bedroom. The 80's was a wild time for religion vs. media.
Getting into the weeds is one of the challenges of writing this (Charlotte's) story. I could end up writing an exhaustive takedown of religion if I'm not careful, but... as you rightfully point out, this is supposed to be a porn game. These things can be touched on to give a nod to the era but... There's a reason Charlotte stops quoting Bible verses after that first quest. I will say that later on, we will get a televised, tearful Jimmy Swaggart-style public apology from Charlotte's favorite TV evangelist because of a sex scandal.
