Mil long post sorry

Ok so let me start this with saying I do not hate my mother in law. BUT she makes me so mad! My sister in law ( her other daughter in law) is one of the sweetest most kind women I have ever met she's been nothing but kind to my husbands family but she does have rules when it comes to her child and my mil cannot seem to understand that. So long story sorry my SIL had a VERY difficult pregnancy and spent quite a bit of it in the hospital. She would post a lot about her situation giving updates to the people who were curious and worried about her and my MIL would constantly and PUBLICLY mock and complain about her posting things saying she was over reacting to everything (my SIL was literally hospitalized and could have lost her little boy) now my BRL and SIL were very polite and calm when they asked my MIL to please stop saying bad things and mocking her but my MIL continued , now fast forward to the baby being born and my SIL had pretty severe post partum anxiety and depression and was very protective about the pictures and types of things shared about her baby on line. She was very upfront and clear about what she wanted and made sure to let mi MIL know about her struggles to avoid confusion or upsetting her BUT my mil chose to ignore it all and posted a bunch of privately shared pictures of the baby on her public Facebook. And when they went to visit the baby she would constantly take the baby out of my SIL sight and move him with out warning my SIL causing her pp anxiety to spike. Ok so I bet you're all asking what this has to do with me? Well my SIL and BIL confronted her about both situations and how it was far from ok and that he was their child and that she needed to respect their rules and she went BALLISTIC she told them they were no longer accepted as part of the family and SHE uninvited them FROM MY WEDDING!! And even when my husband and I told them they were welcome they didn't come because she made it very clear she would ruin the day if they did come and they didn't want to mess up our special day and now my mil constantly tells everyone who will listen that my SIL is a horrible crazy person who's ruining my BIL and she makes jokes about taking their baby away. She's constantly talking bad about them to me and trying to ruin my husband and mines relationship with them like she's gone as far as to try and prevent us from moving near them. She tells everyone that they are ignoring the family but in reality she pushed them away to the point where they don't feel comfortable trying to be involved anymore. She keeps trying to drag me into it and talks about how i better not be like that and let her have whatever she wants with my kids when I have them. She's an extremely controlling person and gets extremely mad when any of her adult children make independent choices with out telling her. I'm so worried because I know I'm going to be very private with what I share about my baby online (currently TTC #1) and that I'm very high risk for pp anxiety and depression and I'm just worried that she'll do the same to me once she realizes she has no control. And I have tried to talk her to not drag me into the drama and Iv told her that I love my SIL and will not put up with the lies yet she doesn't listen and still tries to talk to me about it even if I ignore her.