haunting
eerie
the one-line answer
Passively lurking in someone's digital space after ending contact.
Haunting is watching someone's presence online without contacting them. You watch their stories. You see their activity. They sense you are there without you saying anything. You are a ghost in their digital space.
mainstream
Your coworker might use this word.
01 / in the wild
hear it move.
observation
she's still haunting. third story watch this week.
She is still watching his social media despite having ended contact.