Tate - I struggled a lot with this myself. Part of me wanted to scream my pain and betrayal from the highest rooftops and receive the support and comfort of those around me who sympathized with me. The other part (which won) wanted to protect my WW from the immediate consequences of her actions. Those immediate consequences would be (presumably) hurt to her relationship with our adult children and hurt to her reputation in the community. Additionally I felt that she would see this as a betrayal of HER by me and it would reduce the chance of any reconciliation.
Fast forward 3 months and a bit. The A is still ongoing - not sure how actively though, WW has moved out and is (I believe) on her own trying to get her act together. The A is still (largely) secret although I have told my brothers and their wives with strict instructions to keep it to themselves. I only told them because I needed more support than what was available from random people on the internet (ie this forum). WW knows that I have told them and that they have said that they would welcome her back into our extended family. I "believe" that WW has respect for my actions and is grateful for me keeping her secrets. In a recent text where she said she was going to tell S22 "everything" I responded that it was her story to tell, not mine and it was up to her how much if anything she told. I honestly have no idea who she has told but know that it's mainly been close friends only. To the best of my knowledge S22 and D24 still don't know.
I hope that helps. Adult children are a very different kettle of fish than yours I'm sure.
On BD H52, W50 T27, M26 S21, D23 BD-9-Mar-16 D-15-Jan-18 Final-19-Apr-18 I am a storyteller. The story may do you no good. But a story is never for the listener. It is always for the one who tells