My decently departed mother in law was like that!
She was a very bitter woman.
She deliberately tried to make life miserable for everybody else. She certainly was miserable. I felt sorry for her.
When my son and her grandson was small, I tried to be kind to her, when I could find an occasion. Otherwise I simply ignored her. I never responded or played her psycho games. According to her husband, my beloved father-in-law, the fact that I responded in a bored polite matter of fact voice, no matter what she said to me, made her furious.
Interestingly, shortly before she died, she apologized to everybody she could, for being so nasty!
She said that she wished she had behaved better. She said that she always knew that she had been nasty to everybody and that it had been deliberate, but never said why she was that way.