I can give you several examples, but first, here's a quick "definition" (I'm big on defining):
“Gaslighting is the systematic attempt by one person to erode another’s reality. This is done by telling them that what they are experiencing isn’t so – and, the gradual giving up on the part of the other person.” (
The Gaslight Effect: Don’t Be Afraid To Speak Your Truth by Robin Stern.) So one spouse is purposely speaking and acting in a way to make the other spouse second-guess themselves, their views, their memories, and what they KNOW took place!
Some common examples (not necessarily related to affairs) would be:
A wife SCREAMS at her husband and calls him harsh names and rages in a way that is clearly abusive. Two days later in MC the husband is relating what occurred and the picture of calm and poise, she says, "Oh honey now you know it didn't happen that way. Do I come across like the kind of lady who would act like that? Really? I think you maybe were kind of sensitive." And he knows that in real life she DID do those things, but part of him begins to second-guess if he did just take it wrong.
A wife is walking down the sidewalk with her husband and another male person walks past her. She looks up, meets his eyes, smiles, and keeps walking. "Who's that?" her husband says. "One of your lovers?" "Who?" she says, honestly confused. "Don't act like I didn't see you flirting with that guy. You practically seduced him here on the streets!" She knows she did nothing of the sort, and yet starts to second-guess looking up or smiling.
See how the person knows for a fact that the event did occur, but begins to second-guess their reality or who they are because of the way they are treated?
Here's one from my real life (with exH):
I have a video tape of hubby and his mistress entering a hotel at night (date stamped) and another of him and his mistress leaving the hotel the next morning, all smiles and kisses in the parking lot. I confronted him, played the tape, and he said: "How did you do that?" Confused, I said, "Do what?" "Doctor the tape to make it look like I had been there with another woman. Do you know someone who can do that kind of work?" (My mouth DROPPED to the floor--he's kidding right?) I said, "I didn't do anything to that tape!" "Well you must have done something to it to make it look like me."
(Thankfully I was NOT fooled by this attempt to gaslight, but it was a GENIUS attempt, wouldn't you say?)
Some typical Affair Gaslighting:
The loyal spouse finds sexts, sexy emails, photos...maybe even catches them in the act...and the disloyal says, "How
DARE you accuse me of cheating by breaking my trust and snooping on me! Do you really think I am the kind of person who could do something like that? You must really be sick to have so little trust." (See the attempt to make the loyal think they are mentally ill?)
A loyal spouse exposes the affair to the boss at work, so the boss and put a stop to using the company laptop and company cellphone for sex. The loyal shows the boss proof of emails from the company email address. The disloyal spouse says, "How
DARE you drag my name in the mud and try to ruin my reputation by bringing our private problems here to work! You just want revenge because I've finally stopped taking your abuse at home!" (See how the loyal is just telling the whole truth so the employer can act to protect the company, and it is the disloyal's ACTIONS that may or may embarrass them? And see the gaslighting to make it seem like the loyal is abusive?)
Once they've moved out and you expect them to pay child support and/or care for their own children half time: "Oh it figures all you ever think about is money and yourself. I am trying to get away from your manipulation and all you keep doing is trying to punish me." (It's not punishment to be responsible for your own children. But see how the DS is trying to portray the LS as "sick"?)
Spousal Gaslighting 
Helping couples recover and reconcile after an affair or keep their marriages affair-free at 
