That kinda sorta already exists though. Everyone you can talk to has a bunch of standard dialogs they return to. Once you see a couple of those in a row, it is a good indication to do something else for a bit.One thing that might help here would be some kind of indicator that new dialogue is available for a character - maybe something like an exclamation mark on the chat button.
Granted, it won't help if people just progress to the next event via cheats, but it will help if the player just doesn't talk to Dani anymore because they assume they've seen all of her dialogue.
Sure, not as clear as a marker, but how would Sammy know they have something new to say without talking to them? And these are supposed to be her friends and classmates and such. Shooting the shit for a bit without it being a booping quest every time should just be a part of daily life, no?