I think its all Marilyn from the start. She chose MC smartly.
All her actions are too suspicious, she tried to set up MC so that he get cought by Chloe. (Not just once)
She even insisted MC that he won't be having both of them(Nicole and Chloe) and made Chloe vanilla with MC and all wild and slutty with Beeman.
All her dialogues about Chloe cheating are directed to hurt MC's ego that he lost to Beeman or how Beeman is better with Chloe so that MC give up on Chloe.
I think she is planning something bigger