Do I tell her about the affair?

Your OP suggests you know them because you cater for them or similar? Then later you imply you attend family dinners etc as though you're personal friends?
If the woman is a friend of yours who you have a relationship with that would exist if you were not with her in a service capacity, then that's different from a business acquaintance.
The latter requires a professionalism that would preclude involving yourself in clients personal affairs. If your morals mean you struggle with that, then you should stop working for them.

It is an awful scenario. I bet the wife probably already senses or suspects something. I'm all for telling her, I only say that because I WAS her. My exH was having an affair, his family knew, my MIL knew. Nobody thought to tell me & it was extra humilating knowing everyone knew, but said nothing.

There is nothing concrete to say. Mind your own business as You've only heard rumours. Pretty unusual of your DH to be so interested and involved in the gossip as men usually mind their own business in these matters, does he fancy the alledged OW? Or maybe your DH is the one cheating and bizarrely testing you.

If you don’t want to do it anonymously, could you do it in a way that you look stupid rather than involved to reduce the chance of it damaging the business?

If you said something to her like “ I’m so sorry to hear that you and DH have split up, I hope that you’re doing ok. Is there anything that I can do to help?”

If she says something like they’re not split up then look really embarrassed and confused and say “oh god, I’ve said the wrong thing, on no” a few times. And ask her if they’ve opened up the marriage.

That would open up the conversation and wouldn’t be a completely out-there thing to assume off the back of him having a girlfriend.

This. As someone who has been in this position. Tell her. Many people underestimate the gaslighting, lying, confusing messages that you receive as the spouse in this situation. Whilst you are running yourself ragged, working, looking after small children, pets, co- ordinating activities and play dates, ensuring time with your DH etc you notice things that don’t add up. It’s a crescendo that messes with your head. But you don’t know. The doubt and questions, in the face of his inevitable denial, make you feel you are paranoid or insane. Tell her.
I don’t understand the contradiction on here between all the threads advising women to LTB on the basis of unconfirmed suspicions, and the don’t tell brigade.

Wouldn't say a thing. Everywhere I've worked, there's been the odd situation like this, no interest in rocking other people's relationships or interfering in them.

I would feel differently if it were a close friend, and I knew I could support them emotionally, or it would be worth risking the friendship.

Usually in these situations, the messenger is blamed, the husband digs in and can just either deny it or they 'try again' and even if they divorce, who is to say she is going to be better off if she has young children?

I just don't mess in other people's relationships, I'm not the morality police, I know hundreds of people through work and over the years, I'm not going around telling on them if they get up to undesirable stuff.

I do think sometimes people live in active denial, one of my relatives swore blind she didn't know her husband was cheating, but he was doing it in very plain sight, everyone else had clocked and it was very obvious in terms of his behaviour, I never got to the bottom of why they weren't suspicious when he started taking holidays with another woman! Or disappearing off 'to work' on Bank Holidays.

Jesus, all these people saying don't tell her. Where's everyone morals.

Tell her of course. Either do it anonymously or get a friend to do it anonymously if you can't muster up the courage to do it. Or pretend you're an employee at their company or something, of you're worried about her wondering who it is, but don't give a name.

But absolutely tell her.

I was in the same boat as you OP but with a close friend.... turns out she knew all along and was turning a blind eye. Fast forward a few years, they are still together and he is still playing the field. I however lost a friend as I "knew too much".

Morally you are absolutely right to want to tell her but just beware, you could turn out to be the bad guy (even though you are not) x

Don’t be the one to tell here.
So many others clearly know directly & for whatever reason have decided to say nothing.
Stick with their decisions.

Mind your own business, she may already know. His parents may be hoping it will fizzle out and don’t stop going to parties with your husband. Look after your own marriage and spend time with your husband.

Maybe she is aware of the situation, maybe not. It is 💯 not your business, the messenger gets shot.

I was cheated on and the worst part was knowing that everyone knew but me. I really wish I’d known because it would have changed how I lived my life (I wouldn’t have got a big joint mortgage for a start). I’d tell her in a heartbeat. I wouldn’t be protecting a cheating bastard for a single moment.

She could know, and be quite happy living a nice life with her two kids and has decided to turn a blind idea.

Maybe she's happy he's occupied with another woman? Maybe she couldn't give a shit and has just accepted the status quo??

Who knows

I can’t believe any woman in that situation wouldn’t know. But the fact is it really isn’t your business to tell her and you don’t know what goes on in their lives. I also think anonymous letters are very cruel and creepy.

No good deed goes unpunished, I would not risk my business over what strictly speaking isn't my business. I applaud you for your empathy and moral compass, though.

If you truly think you can deal with the aftermath and want peace of mind tell her anonymously, making sure it can't be traced back to you.

Ffs. I’m so frustrated with the “don’t tell her as she probably knows” crew. Yes, probably everyone knows and she has an inkling. Probably driving herself crazy as she has no proof and is second guessing herself. If she already knows what’s the problem in telling her. If she doesn’t know, what’s the problem in telling her (esp if OP feels she can afford to the fallout).

You must know by now precisely what happens to the messenger… I know it’s awful but it really isn’t your life and you shouldn’t go tampering, it won’t end well. She might already know and be intentionally ignoring it.

Yes true! Maybe shes playing along as it bring out in the open might force a decision that shes not gonna like 🤔

I simply do not care to make other peoples relationships my business, and I don’t expect anyone else to make mine theirs.

By telling her OP risks it blowing up in her face, not his. He’ll be fine - he’s employed by his parents and they will almost certainly minimize his losses in any divorce IF it happens. Op however could blow up her own relationship if her husband isn’t on side and/or their business if their current partners are connected enough to have them blacklisted. Even if they aren’t, future clients are not unlikely to be leery about working with someone they can’t trust not to stick their nose where it isn’t wanted and expose their moral transgressions.

i dont think it matters what others think about how reasonable or unreasonable it would be to tell or not to tell this poor woman shes being made a fool of.
I can understand why you feel conflicted given the bussiness connections and not knowing what this woman knows or doesnt know.
If you tell you may be shot as the messenger,disbelieved or your bussiness may suffer.
If you dont tell you live with those feelings of discomfort.
You could consider letting her know anonymously .

Would you feel the same if it was DV? Or financial abuse? Or incest? is it just knowing a woman is potentially being exposed to STD and having sec with her husband his deception that is ok with you.

some lawmakers consider having sex with somebody knowing that they wouldn’t have sex with you if they knew that you were also sleeping with someone else sexual abuse

but it seems some people out there like you think it’s absolutely fine to know that someone’s being abused and say nothing

I'd write her a note and post it to her.

As someone who was cheated on by x and a work colleague, she probably has an idea . I would not say anything .

I would let her know anonymously. But in a nice letter saying that you think she's lovely and deserve better.