As I always say I can only speak for my own situation with my mother in law. I do know that it took a lot for me to say that is enough I won't be treated this way any more. Before that I just sucked it up and pretended it wasn't happening or that I hadn't heard the belittling remarks and snide comments.
Sometime after my second child, when she was perhaps 2 years old, I just stopped dealing with her anymore. I didn't make any announcements, ask my husband to speak to her or anything, I just stopped going over, stopped inviting her over and just stopped dealing with her at all. If my husband had her over, I was generally not home. Suffice to say she noticed, but she's never made any attempt to find out why. That tells me she doesn't care enough to bother with me. Why would she? She can see my husband and children (not so much children any more though) without the impediment of having me there, only it doesn't quite work that way.
My husband doesn't visit, he's free to do what he wants but he doesn't go there. We rarely discuss her. Recently she had a fairly major surgery, I didn't know until weeks later. My husband was phoned and told by his father, he was told to also let his brother know. Well he didn't because he says he is nobodies messenger boy. He also didn't visit her at hospital. I don't know why? I visit my ill relations, I don't drag my husband with me. Perhaps that is why he didn't tell me about the operation? Perhaps he didn't want to have me suggest he visit her? I don't know. I do know that before I gave up, she got a lot more time with my husband and my kids. Apparently that doesn't matter either though, because she makes no effort to fix the relationship. Nor any of the others in her family.