Hi ((((Rose)))) ugh. I am sorry you heard any of it I empathize with you...certainly puts you in an uncomfortable position.

What comes to mind for me is what kind of supervisor, person in a place of authority, would do such a stupid and childish thing?

If there is an hr, risk management, division at your place of employment, whatever the reason, I am quite sure they would not take this type of behavior lightly.

That said, unfortunately, I dont think there is much you can do short of encouraging your co-worker to speak with hr. Especially if it is still troublesome or is creating work stress.

It is your co-worker's responsibility to report the action to hr if it is an issue. HRs responsibility is to take it from there.

Best wishes to you.