@chirco3 The mother in law here is not taking any responsibility for her part in making the son choose. Until she does that she’ll remain estranged.

My sister’s now mother in law was a real problem when my sister and her now husband got engaged. The mother was truly awful and said terrible things about my sister. She didn’t want her son to marry my sister because she couldn’t control my sister.

My brother in law told his mum to pull her head in or she’d need to stay away and miss out on grandchildren. His mother behaved much better. No doubt my brother in law in private also helped my sister to relax and come off the defensive. Mother in law and my sister grew to have a mutually loving and respectful relationship - but the mom still at times needed to be reminded where the boundaries were!!

Mother in law here needs to have a good look at her own behaviour. See if she can make changes to build bridges. Or accept the estrangement and move on.