I don't understand people and the NTR tag. If you watch porn then you are watching a guy fuck a girl (assuming a standard porn situation). Does that trigger people?
Sandra was gang raped 12 years prior and hasn't been close to a guy since. How is that NTR?
If a woman mentions her former boyfriend is that NTR now too?
My one objection about the Sandra revelation is how quickly she trusted the MC with it.
Ugh
That's what pov is for! Ok, if I have to give a serious answer, in most games (actual games, not kinetic novels) you have to make some choices, so it's easier for people to immerse themselves into the MC's place. Porn is just jerk off material. I don't think that there are many people watching porn for the storyline or to immerse themselves into the "protagonist's" place... It's just two or more people fucking. For instance I don't mind watching dp or gangbang scenes in porn, but I won't play games with unavoidable sharing, even if we are talking about just one scene that only lasts a couple of minutes.
About the ex boyfriends, I agree with what darth_hiruma said. It becomes a problem only if she starts giving you "details" you didn't ask for.
Now, about the issue at hand. I personally don't care about the "incident", meaning it doesn't make me want to avoid Sandra. I like her, so I'm going to pursue her and if we get to beat the crap out of the guys, even better. In general I don't like this kind of storylines, but the fact that it happened in the past makes a difference, at least for me. I think the problem for most people was the way she talked about it. In these situations you want just the facts. "They raped me and even laughed about it" and that's it. Everything else just creates unneeded mental images. Saying how they took turns raping her for several hours was a bit of an overkill. I think that even if a woman decides to talk about such a traumatic experience with someone she barely knows, she would still be reluctant about sharing some of the more painful details. I might be wrong, because like I said it's not a dealbreaker for me and I actually liked the game, but that's how I see it.
I just want people to know we're open to listen but we don't want to hear the worst that we've been seeing 
