In Anna's mind, she is fully in control of her actions and thinks it's ridiculous David wouldn't trust her. If a man hits on her, so what? She will tell them no thanks and move on. When David gets upset or jealous she finds it unattractive and irritating.
You are the dev and made this character, but the described personality above doesn't really match her actions too well in my opinion.
Its an NTR game, so something is supposed to happen. But let's be honest here, no need to blame everything on Anna's openness, naivity, and desire for independence, because:
That's actually not, what Anna is doing, when Chris lovebombs her with compliments and his naughty thoughts about her. He's quite frank about expressing his desire for her and he tells her also, that he doesn't care, that she's in a relationship. She says nothing will ever happen between them, but her actions tell another story.
She might say "stop it", but doesn't mean it. After all she lets all his heavy flirting attempts pass. She even sends him fotos of herself in a nightie, even 2 or 3 of them as far as I remember, so that he can fap while watching her pics! Which faithful wife would do so seriously?! That's definitively a no-go already. The reason behind is not just naivity in my book. She clearly doesn't say thanks, I'd rather not and moves on. She also doesn't give a real stop signal, like threatening to break up contact, if Chris doesn't stop hitting on her. Let's keep in mind, she is supposed to be recently married, happy with her husband in general and also pregant from him.
Furthermore, if she's got such a great desire for proving herself in front of males and showing her independence, it's rather strange, that Crhis can manipulate her that easily into doing naughty stuff, she doesn't want to do or at least doesn't consider to do in the first place without triggering her resistance. For me there are some logical gaps in that story.
So after analyzing the week from David's point of view, one can only come to the conclusion, that Anna is really not an innocent girl. I guess part of her even enjoys it, otherwise she wouldn't go that far and let all the hitting on her pass. She even gets involved actively by sending those erotic pictures of her, which tells us, that she somehow enjoys it, if another man or maybe just Chris faps while thinking about her.
Part of her personality is clearly leaning towards attention whore behaviour. This would cause a serious crisis in most monogamous relationships, if the truth would come out someday... Most likely many, if not most guys would say fuck off for good to someone like Anna after such actions.
(In real life it makes no sense to argue with such girls, they need the male attention for their self-esteem, it's part of their personality and therefore they will never stop. So best is really to just quit them / end the relationship, if you want another kind of relationship. That would be based behaviour, otherwise she'll turn you into a cuck.)
But back to the game,
I think, in the end her personality has got a somewhat darker side than the above described. Sending those pictures of her in a nightie to another guy is too much for someone, who is supposed to be happily married, rather innocent or just unaware and naive... That doesn't mean, I'd suggest to change some of the story so far, I'd rather advice to be more honest about her personality. Because the naive, but independence seeking girl with a strong will, who is happily married so far, doesn't match with the little somewhat slutty attention whore, who sends pictures of herself in a nighty as fapping material to another guy in the middle of the night, while her "beloved" husband is right next to her sleeping in the double bed. Therefore the writing so far isn't that convincing for me. It only makes sense, if she has got a somewhat darker personality and maybe a low self esteem, so that she secretly very much enjoys being hit on or a borderline personality disorder or daddy issues, whatever.
My concern is not about NTR or NON-NTR, because this game will feature NTR for sure, my concern is just about making it happen in a believable way.