I guess she doesn't know that. We also have postings.
Yes, indeed. It's a good thing to remember... deleted posts aren't actually deleted, not from your emails, either btw. Nor are your call and text logs, although in come cases texts may not be retrieved.
That's why it's really important to be prudent about writing anything that could be interpreted as threatening someone, or wishing them violent harm. Should something happen to them that even vaguely resembles what you said, you could easily become a suspect in an investigation until proven innocent... which is a horrible stressful experience, and very scary.
I have not had this happen to me but I have been part of a number of situations where in a professional capacity I had to review such materials. It makes me willing to be occasionally snarky here but NEVER threaten anyone or specifically wish them harm. Once it's posted, it's out there, gone, and in the vast majority of cases you can't delete it. Same with my emails... I won't but potentially problematic things in writing, will deal with it directly instead if need be. That's just me, but I think it's helpful information.
Never write something that could come back to haunt you in the future legally or that you will regret saying if questioned about it by the authorities, it's a hornet's nest to deal with that. Just saying...