My initial reaction is a true friend wouldn't do that.

Then I remembered I once unfriended someone I liked and cared about. It was bad of me to do. I was confused and not thinking straight. The person I did this to deserved better. She forgave me, we are still friends. I was lucky.

I guess I am saying sometimes there are reasons we don't know about why someone does this. Sometimes forgiveness can be appropriate and a blessing. Not always but sometimes.