Heard my X might marry OW. Felt sick to my stomach, but the feeling passed. I've had some minor health issues lately and really can't afford to stress. I think I'm better than I thought I would be by now, but not yet at complete 'meh'. If I never reach total detachment, I still know I will be ok. The experts say that day will come, not going to rush it, just accepting where I am right now.
I understand the ideal goal is complete detachment and to not care at all what your Ex does, but in real life that's not so easy. I think most hearing an ex-spouse was going to marry (especially to an affair partner) would not feel great about it. It is the person who promised to spend the rest of their lives with you and you had children with. It's understandable to be upset by the development. So...don't feel bad about having the "sick to your stomach" feeling. It too shall pass and processing through it will actually further your detachment.
Me:39 Ex-W:37 M:7 T: 9 S:6 D:3 BD/IHS/Confirm EA/PA: Feb '20 OM1 affair ends: May '20 W/OM2 & moves out: June-July '20 W files for D: Jul20 OM2 confirmed: 9/2020 Divorced: May '21