Actually she did indulge in incest before, she admits to the shrink she had some sort of sex with her brother, and she only commits incest in this game if you use the incest patch.You say the core of her morality isn't changing. But how can that be the case, when she's allowing herself to be sucked into a relationship with Marc, having sex with her dog and horse, and cheated on her partner? All things that she would have previously considered to be reprehensible. She's doing so many things, that she would have never dreamed of doing in the past. Which her former self would have been horrified about, if someone else had suggested that she was going to do those things in the future. The reason why she's able to do those things, without feeling really bad about it, is because her morality has changed. She's become more open to doing things, that a large chunk of society ( including her former self) , would view as immoral.
How many times in the past did she tell Marc, that what they were doing was wrong, and they couldn't do it again? Does she say these things anymore? She doesn't because her core of morality has changed
Women in adult games are caricatures, they don't bear any resemblance to women in real life. Myriam for instance is a nympho slut, and has more sexual partners in one day, than the vast majority of women in real life, have in their entire lives.
I get that her personality isn't typical. She's intelligent, generous and caring, and not just the usual sex-crazed bimbo who often turns up in these games. But Myriam is one of the most promiscuous characters in adult game history. So she's still stereotypical from that perspective. She basically has sex with virtually every person she meets, and you can't get more porn tropy than that
This is not correct. Prior to this game she wasn't indulging in incest, she wasn't having sex with her pets, she wasn't having lesbian sex, or gangbangs, or cheating on her partner. The example you give is irrelevant, because her attitude to incest has changed completely, from not doing it at all in any circumstances, to doing it regularly with at least one person. And your interpretation that she's already interested in these kinks, but just not exploring them, is simply not true. At the start of the game, Myriam thinks most of these kinks are wrong, and that normal people don't do them. She changes her mind about this, because her sense of morality is challenged by people that she trusts, like Evelyn and Edward
She doesn't have to cheat on her partner, that is your choice for her to cheat if you can even call it that, after all she doesn't 'cheat' until after catching her partner cheating (raping his secretary).
No one has forced her to have sex with her pets except herself, except for that rapist Cassius, although Hammer did force himself on her the second time, but at the same time you as the player always had the choice whether to go there or not.
So, she had sex with her brother in the past, she seduces her high school coach in the past, so she has previous in the things you're saying she didn't. Her own partner/husband basically forces her in to her first gangbang, a lot of women after a split from a long term partner have entertained the possibility of a lesbian relationship, but yet again it is, as the player, your choice.
And with Marc, yet again, it is your choice as the player what sort of relationship she has with him.