for Arbor's route
1st meeting
"did you draw those?"
2nd meeting
"looks like you really enjoy this"
and then try to go to the afterlife by dying.
you can eat the mushrooms in the forest, it's the quickest way to die.
I think you only need to eat it 2 times tho.
but after death, there's an option where you pick to just die or still live(as a ghost), if you pick the live as a ghost one. You'll continue to Arbor's route.
Also it may be better if you save at this point, where you pick to pass on or still live(as a ghost ofc)). If you don't want to redo her route all over again(if you choose to pass on by accident)
this may be somewhat incorrect but this is what I remember from playing in her route.