What would happen if yuo stood up to her, in front of him (would be great for your sons to see you do that!). What if you assertively said, somehting like, I dont think you should speak to him that way, he is a grown adult now? Would she be shocked??
I have to disagree Ali, imo that would be showing massive disrespect for w's mothering skills and would undermine each other as parents. A big no no in my book (not that I have children , so I may not be best placed to pass judgement on this )