Mother-in-law Hell

My MIL is one of those people who honestly believes her ‘problem’ is the she is incapable of getting angry. She is forEVER telling everyone this, and she really believes this about herself. Unfortunately, she shows her sweetness in caustic, nasty ‘helpful’ remarks and gossip. I used to see her as pitiful, however her gossip has gotten so destructive that she actually succeeded in manipulating my husband and his brother into seriously disliking each other ( until they got smart and figured out what was going on). Dh’s niece, who is close to MIL, will not even speak to my husband in spite of the fact that we NEVER see her. How do you get that angry at someone you have not spoken to in years, you ask? Could it be you are too young to know not to listen to the idle gossip of a silly old woman? The last time we saw this niece she was at our house moving out furniture we were giving her for her first apartment!!! ( Still waiting for the thanks for that but…)
The final straw with us came when this niece got married. She made a point of not inviting DH or I to the wedding. Not a big deal - as I have said - we are not all that close to her, in fact we did not even know it was happening. HOWEVER MIL could not wait to call DH the next day to tell him ‘I told people at the wedding you were not invited because you do not like family invitations’ Mind you - half the people there have been guests in our home many times over the years…she then went on to tell him that she later apologized to everyone for saying it.
What kind of a Mother does this to her son? The woman is certifiable.
There have been a lot of other incidents - you will probably hear more in time, but that one did it for me. I am now finished with her. I will be polite when I have to, but I am done. Thanks for letting me vent.