If it were a newbie, it's more than likely Falynn. Adventurous self.
But Marlo, when she's drunk she really has no self control. Like when they were in Barcelona grinding up on one another and in Tokyo it looked as if she didn't even know where her hotel room was.
It's gotta be them 2 (Porshit & Marlo) because they both get confronted the following day by the group and Kenya was said to be gagging the whole entire time about their secret rendezvous.