Yeah she gives off way too many red flags combined with her obsession over MC and weird remarks like it was his fault she went to prom with Ethan, like she blames him in a way as well.
Now all explanations can be innocent and she is still blind to fact Ethan is an asshole who has likely curtailed her social circles a lot on purpose. Well depending on where Nyx wants to go she can also be a heartless bitch that likes her luxury and is all about her and has happily worked with Ethan fucking up others with a weird obsession for MC and he will be way better off without her.
So for the moment i will just wait and see and accept that the MC I play has feelings for her, whether those are more of the romantic kind or more those for someone that was in many ways like an older sister for him. If it was up to me though my MC would shamelessly go for Alexis or Melissa if she was an option for a serious ending.
Layla would be next option, but she will kinda clash with Alexis and Alexis ending might be kinda bitter if played Layla as well and knowing her story. Yeah for me my MC does not owe Erynn anything romantically and she will have to earn it still, even if I know my MC might disagree.