They all do pretty awful things ICF. Not to diminish the effect of what your W has done. It is pretty despicable and if it wasn't so hurtful, you could roll your eyes at how immature it is. I imagine it says more about her than it does about you to anyone reading the comments. I guess we all ask this question sooner or later. And I personally think it may be a factor on whether or not the crisis person seeks to reconcile. The mending of so much damage may seem impossible to them. And, IMO, I think there's an aspect of bridge burning in their behaviour too. Like it's easier to burn everything up, then there is no way back. The question I asked myself was - do I want to be in relationship with someone who did such cruel things to me and did not have the courage to apologise and make some amends? That person would still be broken, IMO and therefore, the relationship would fail again. So, as simple as it sounds, they either do or they don't. And we can't control that. They have to do their own reflection and healing.
Sorry it's so painful and you have to endure this. Try not to engage with the 'monster' who posts on social media. As in, don't read the posts, and tell others you don't want to know. You will find more inner peace.