If married, I’d stay and smile as long as it took to gather all the evidence I needed for court.
If unmarried but living together, I’d stay and smile until she left for work, and have all her shit sitting on the street when she returned to find the locks changed.
If unmarried and not living together, I would immediately cut off all contact and let eternal silence do the talking.
If she cheated on me with a friend, and it was a regular thing, I’d call Cheaters and make a buck off of my story.
Of course before any of this happened, I’d make sure to put her phone number and email on every solicitors list that I possibly could.
Nah… Just kidding. I’d probably just disappear.