Thanks for bringing this to my attention! I'll look into it asap.
Routes are decided by the choices made at the welcome party and at the bar with Wyatt. After the reunion with Freddie, going to the bathroom puts you on the Janus/Will path, getting a drink puts you on the Delilah/Slayton(/Wyatt if you have the DLC) path, and joining the group conversation puts you on the August/Freddie path. Later, when you're at the bar, your choice to stay puts you on the more extroverted person's route, while leaving puts you on the more introverted person's route.
So, for Delilah specifically, get a drink at the welcome party, then stay at the bar for another drink.