Firstly, the dark path is the rape/assault path;
what you're describing (I believe) requires starting on the blackmail/manipulation/corruption/findom path (the 2nd option where you decide what to do with her after her revelation) and then just consistently being nice to her; it's like the "wholesome" blackmail/findom path, I guess it's considered corruption maybe? You should be on her romance path by the end if you keep being nice and doing things that she would want. She's a naughty adventurous girl, btw, and is open to instant apologies and backpedals when you reach just shy of going too far
Anyways, point is you can do that without being on Nicki's dark path. I can personally confirm because I took that option and am NOT on Nicki's dark path, but her romance path
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(my save variables say as much). It may change when Neon redoes chp 1 though. There may also be a few unintented interactions in the code which will also be fixed at that point. We'll see I guess.
Also, don't forget that this game lets you swerve onto other paths with characters (where it makes sense), so even if that phone scene puts you on corruption path, you can easily swerve onto her romance path in the next one or two chapters.