They want a reaction/response. I had an ex friend do this several months ago. With her, and because she was calling me at work and my phone bounces to others when I am not at my desk, I texted her we could "talk at a later time but not when she is behaving so poorly".
She stopped and has not bothered me in 8mo.
Had it not been my job I would have just ignored it. I tried to contact her husband on FB to stop it, only to find he had blocked me from contact. Her mom is dying of Parkinsons and I refused to contact her parents. I was not sure what to do.
This was a friend since childhood that just snapped. It clearly was a break of some sort and I believe it was due to the loss of her child. I did not want to get her arrested or in trouble, yet I already went through this crap with my BPD ex and didn't want to get fired either.
I have had this happen with several people in my life. More than I can count. I am trying to fix whatever is attracting this.
Anyways, to your post

Ignore, Ignore, Ignore.
PW