marina - OW sounds like a real piece of work. It is ok to feel bad for W.
W is letting her speak to her that way because she is desperate, lonely, unhappy, undeserving, guilty, ashamed, etc... One or more or all, in short she is mixed up.
You are right, you can’t save her. She doesn’t want to be saved right now. Besides she needs to save herself.
How can you help? Be that beacon. Raise your kids well. Keep moving forward.
I would like to add something from an earlier discussion. It was about how W was starting to feel the weight of being a parent.
It is possible that W might just offer you all the parental responsiblies. She may just want some visiting access, not custody. If that discussion, arrangement, offer is ever made - take it.
DnJ
Feelings are fleeting. Be better, not bitter. Love the person, forgive the sin.