It's rude to ghost someone online.
Allister was having an online relationship with Betty, but has become bored with it.
Allister wants to break it off with Betty.
Allister tells Betty he wants to move on and wishes her well.
Allister stops all contact with Betty and doesn't respond to any of her messages.
Betty is upset, but gets over Allister, and she doesn't wish him any ill will.
Betty becomes distraught thinking Allister is hurt or dead, and later resents him when she finds out he's fine.