I don't say there's a clear plan(even if there was Nyx has a huge history of changing her clear plans).
Nyx also has an even bigger history of misdirecting players with her comments and is usually mindful of actual serious spoilers so her saying in plain words "Val is gonna get killed by because of Ethan" has all the signs of trying to get rise out of people.
Rachel on the other hand was no one's favorite and had been pretty much written out and forgotten, she was perfect to be used as a tool to raise the stakes, push a "careful with what you chose" idea on to the players.
Imo, she needs a backstory, things that happened to her in the town she used to live... Maybe family history too(Nyx is using with Val's mom the same trick she uses with Layla/Alexis dad and always shoots her from the back, always obscuring her face)... and those need to connect to her current personality/attitude.
Who were those pics in her phone for?
Did she have a boyfriend who fucked around on her? Maybe backstabbed by one of her friends...
Things that explain is she so non-chalant about shanking other chicks and just "tries" every option available, even Darryl who anyone can see is a douche from a mile away.
She does have the most "wannabe suitors" with Darryl, Zach and maybe the gym instructor...
