should I tell my best friend husband that she is cheating?

I am 32 male, my best friend is 36 female, we've known each other for 12 years due to us both working for my father's company, we were a perfect duo and everyone always taught we were together or sleeping together, I was never interested in her because she had a boyfriend from the start and I knew him. in 2015 she got married to her bf and 2016 I got married to my gf, we both attend each other wedding. fast forward to 2022 I got promoted to supervisor of my father's company and she also got promoted to manager of her department but we had to travel to a remote location to work, this is where everything change.

we started spending alot of time together and I noticed we were becoming emotional attached, I started noticing how attractive she was, I've known this woman for 12 years and only now I realized she is a 8/10 in attractive, but I fear losing my wife more than my immoral desires, so I decided to tell her that we are too emotional attached because we are away from our partners and we should be careful, and she agreed. At this time I thought that was it then came this guy that looks and act similar too her husband.

A little bit more info on how our work is scheduled, we are away for 10 days from our spouse and we are with them for 4 days when we get back, we all live on a campus and our rooms are close together, we get a 50% increase in pay, with that my best friend earns 3x more than her husband and my wife is a stay at home wife.

So this guy let's call him KV he started watching her alot, she noticed him always watching her, so she told me and I told her not to bother with that too much because she is married, but without my knowledge she gave him her number, so one night we were smoking and he was texting saying he wanted to talk to her, so she told me she wanted see what he had to say but she would call me after to meet up back. She never did.

She eventually told me they had sex after the 3rd day of talking to kv, I was honestly disappointed but this is where it gets crazy, kv is also married, and on that weekend we all went home to our spouse, but my best friend though somehow they were in a relationship so she started calling him alot while he was home with his wife and he decided to block her, kv taught she understands that their relationship is only on when they travel, because both are married. She call me drunk crying because he blocked her and asked her where she was and amazing she was home with her husband, so I told my wife I got a meeting which I did but I left a hour earlier to pick my bf up because I didn't want her husband to figure out what's going on. While with me she was throwing a tantrum and having a panic attack for being blocked, being as attractive as she was she was never rejected or dumped before.

I was afraid her husband would notice these behavior because she was really going crazy she could not walk without crying. I decided to call kv and explain to him if he cut give her closure. He agreed and when we got back on our travels those two got back together. I started getting angry at myself because I taught this would end but it continues and guess what happened the next weekend when we had to go back. She throws a smaller tantrum, I wanted to tell her husband but I don't want to ruin someone's life they have two kids together.

I'll try to wrap this up am getting tired So kv and my bf eventually broke up because she wanted girlfriend treatment and she wanted to control him and wanted to be above his wife, but he was not having that eventually he got move back to the city because his supervisor found out about the affair,

After a few months she started talking about the affair openly with coworkers and it eventually got back to her husband the week before he travel, she begged him not to leave her, he says he will come back and she shouldn't worry, that one month he was away she was completely faithful but have panic attack ever so often if she see a unknown woman in his photos.

Her husband came back and they reconcile and she promised to be faithful, she took 3 months off from work now that she returns her rooms is no longer available because of over booking mistake, her AP company said she can stay in their house for a bit until it solve, now another coincidence happened KV returns to this house the same time to work so now they're living in the same house, remember her being faithful from now on? Only lasted one night, her husband doesn't know this but kv been blowing her back out two weeks now and this morning she is bragging to me that she didn't get enough last night, I ask her why not just get divorce and do what you want after, she told me her husband and her kids is everything to her and kv has his wife, I am tired so tired of this I just want to tell her husband I really do, I can't even talk to my wife about this because my wife would immediately want to ban me from her.

I just hope her husband grows a pear of ballz. My goal was to make her see her mistake and change without her husband noticing her cheating but this is too much on me

UPDATE: thank you guys for those wonderful advice and those insult too I guess. I came to my decision earlier today, this will be the first and last time I give an update I have a meeting at 7 tonight and I only gotten 3 hours of sleep.

1. I told my wife about the border line emotional affair that we had that I stopped from developing further, the lying to meet her before going to our meeting when she was having a meltdown, noticing how attractive she was from spending too much time together, and hiding from her that (ML) was cheating. I now Have to refer to her as (ML) I cannot call her bf anymore,

Wife: yeah I know I can see 300 plus reddit comments in your email Although am upset about you hiding such things from me am more concerned about the effort you go to try to save someone who doesn't want to be save? Currently being scolded

2. I contacted my father about our work hours and if we can cut it in half, so it don't affect our family too much someone mentioned about this 10 days work hours affecting family life, maybe 5 days will be better we have a meeting scheduled for 7 with HR and other managers to see what everyone thinks about this.

3. finally the main issues ML), I decided not exposed this to her husband, I read as much comments as I could and ask for the advice of my wife and also my decision the reason I didn't exposed her to my father, this is my parting gift for her as a long time friend. I talk with her and told her I can no longer bear this for her and she understood right away where I was going she apologize for dragging me along in her affair, she knew I always got her back and took advantage of it, she also apologize to my wife for getting me involved, We agreed to limited contact outside of work And that she would temporary transfer after this project is over in a month. I told her I don't care if she an kv continue just don't involve me, now I gotta work to get back on my wife good grace and couples counseling.

So my conclusion is this not my business.

Most will hate my decision but her husband and kv wife will find out they always do

Ps: English is not my first language give me a break