Yeah i read that once around here, didnt ever went that path though... iam not one of those who have to do "everything" to unlock 100%, especially not if it include some dark path iam really not comfortable with.It actually does turn it into NTR If you don't help her but it's off screen if you don't help her while she's being touched up and slapped by Ethan she ends up giving in and having sex with Ethan.
He mentions it when you go with Zach just after Zach punches you I believe but at that point if you're not helping her you're a monster who doesn't like Erynn so it's not NTR to those people but it certainly would be to people who are completionists who wanna do everything even if it hurts them or a character they like.
And even if i wouldnt care for Erryn (but i do, like her some how, way more than alexis), not helping her in that scene where Ethan is harrasing her? Come on... i would even try to help a complete stranger on the street... not that iam a "strong hero" type... i am afraid of any violence. But screaming out loud "help fire over here" does the trick pretty much everytime... Just screaming for "help" doesnt do anything, but mentioning fire? Oh boy you will be surprised how many people are getting to the scene in an instant, even in the middle of the night. Nevermind... point is... i could not go that dark path down, and overall, i think i doesnt really fit the MC too... cause even if you play like you dont care for Erryn, the MC doesnt really "act" like an asshole throughout the game, even if you try... he is way to nice most of the time, and your decisions doesnt really change his behaivior in a way where it makes sense that he simple doesnt help someone in heavy need. Especially if you consider that its Ethan there... cause no matter what, the MC always hates him. Not helping there just doesnt make sense. I think, it shouldnt be an option here... cause it doesnt fit anything the mc is doing so far.