Honestly? She’s there mother. That’s all that matters.
People can say that one day they’ll know, they’ll make their judgements, they’ll dislike her etc but in reality those are cliches which people use to make the hurt more bearable for themselves, because people want others to think as badly as the partner who cheats as they do.
And yet anecdotally of all the people I know whose parents cheated when they were younger and who stayed with the AP, they all have good relationships with not only the parent but also with the new step parent.
I think if the relationship doesn’t last that could be different, but as unpalatable as it is, often when a relationship ends where someone leaves for the AP and that relationship stands the test of time, many people will ultimately admit that that’s just how it was meant to be.
There are even MN’ers here who have said that their ex is actually much better suited to the affair partner, but that realisation takes time.
But don’t be bitter. You’re never going to get gratitude from 11/13 year olds. That’s just not how it works.
And it’s possible that they like him. It’s possible that to them the marriage was unhappy and they see their mum happier than she perhaps was before.
Ultimately the only one you need to deal with is yourself. You can feel free to feel as bitter about her as you like, but do bear in mind that life does go on, and that at some point you will need to move forward. Bitterness is like drinking poison and waiting for someone else to die. It achieves nothing.
And yes, I’d say exactly the same if it was a woman posting here.
I know too many cheated-on people who have spent so long feeling bitter that their children have automatically gravitated to the other partner and in many cases have even had empathy for how the marriage ended.