Had that exact same issue right now with the event not triggering.
Managed to solve it after pulling my hairs for 1 hour looking at the code (Or maybe it was just luck).
- First : Code say the event is only activated in the game after day 160 (mid july), but that shouldn't be your problem since it's also the case for the event where she call you to her home.
-Second : Code ask that you have in your inventory a slut maker drug at least level 1 (first upgraded version)
-Third : Code also ask that you have a train ticket in your inventory, BUT , the code consider basic "train ticket" and "train ticket (weekly/monthly)" to be different items. In the case of this event, it asks for a simple vanilla train ticket.
The event activated for me after I went to the platform (between 6:30-16:30) and bought several single-use tickets before changing location.
Hope it'll solve it for you.