What is her problem?!

Given he is having an affair no wonder the poor woman is insecure. If she knows he is up to no good but doesn't know the actual identity OW then she probably does think it's you. And you don't come out of this at all well given that you are condoning a cheat and a liars behaviour and actually considering encouraging it.
What a mess.

It's not really insecurity if it's founded in reality.

Her husband is having an affair and his friends are egging him on.

I think you came on here expecting everyone to side with you and you're not liking the fact that posters aren't. You do sound quite spiteful and I don't believe you weren't given a promotion because of someone who doesn't even work there. You sound paranoid.

I don’t like your friend.
You don’t like his wife.

we’re all entitled to an opinion.

it seems to me that she has reason to feel insecure in her relationship. She’s assumed it’s you that is getting his attention. I don’t think she’s made a huge jump to reach that conclusion.

If he wasn’t a dick, then you might find she’s nicer to you.

The root of the problem is your friend. But you won’t hear a bad word said against him. You even encourage him. How do you think that makes you look?

Everyone in this story sounds unlikeable. I'd start over again with new characters and try to include at least one normal, decent person.

I think you lack empathy and only consider things from your own perspective. Her DH is actually having an affair so it’s not like ‘he’d never to do anything like that’ because he is. You’ve no idea what else he might have been doing or how he behaves towards his wife when they are at home. He’s lying to her now and I doubt it’s for the first time. Your upset at her apparently disliking you is understandable to some extent but is clearly due, at least in part, to how your ‘friend’ treats her. He’s disrespecting her in his current affair but you’re still hung up on how you feel she treated you.
It’s also not clear who is feeding you the info that she has talked about you in the past or is still talking about you now. It sounds to me like stirring the pot. All the stuff re the promotion, how do you know this?
Your desire to have some kind of revenge is a disproportionate response to all this. It’s unkind, unprofessional and unnecessary.

I’m with you. I’ve had lots of male friends at work over the years with no romantic interest at all. In fact I’m far more like to nag them to be nicer to wives/buy good presents etc but some women always feel threatened. It’s very odd.

It's odd not to have a shred of sympathy for her. You sound quite callous to be frank.

Have you not told your ’friend’ what he’s doing is wrong. How do you know he’s having an affair? He sounds like a dick and respectfully, so do you.

I would love to hear her side of the story.

She isn’t insecure if she’s right!!!

You're unreasonable because you say women should stop blaming other women-it's both the married person and the person they're cheating with who are equally to blame, unless they genuinely thought he was single. I would never sleep with a man who was married/in a relationship, and anyone who does is equally as bad as a cheater. Not just "girlcode" or women expected to be better than men. And your workplace sounds awful if you missed promotion/if people are gossiping like this, but if you've said what you have here, maybe that's why people are treating you like this, not because they think you have slept with a married man, but because you don't think it's wrong other people have affairs with them.

I find it so strange that someone can be that insecure about their marriage that any woman close to him becomes a threat.

WTF?? You've said he IS cheating on her - just not with you.

She's absolutely right to be insecure about her marriage. He's a cheating shit! For all you know, maybe he's using you to put her off the scent of what he's really up to and with whom.

From what I’ve seen, her behaviour towards him is very controlling and seems to have pushed him further away
I wonder if his behaviour has anything to do with how she behaves. Husbands being “pushed away” by their wives is a classic affair excuse.

He was the one who sheepishly told me that she had been discussing me with our boss and that he thought she’d said enough to potentially ruin my chances of getting a job I’d hoped was on the cards.
What a exactly is she supposed to have said? Was he there? Did he not correct things if something incorrect was stated?

Who else is she ‘still’ discussing you with?

I really think you have to consider this man’s role in all this. You don’t know what he’s telling his wife or how he behaves at home. You only know what he tells you and the little that you see.

I’ve actually only met her a handful of times in person and she’s always so fake to my face

Why do you care?

She even stopped me getting a promotion by slating me to our employer

Your employer sounds unprofessional to let someone’s wife slag off their employees to them and have it affect internal decisions.

AIBU to be encouraging his affairs at this point?

Obviously.

I get where you’re coming from, but I think you’re missing the point that your friend and his behaviour is at the root of all this.

Even your thread title

"What is her problem?!"

Surely it's obvious to you what her problem is? She's married to an adulterer.

Poor woman.

Horrible thread !
And why post on here ?
Your not really asking anything you don't like this woman she doesn't like you
Her husband IS having an affair not with u but someone else and your happy for her to been torn down by all this because I don't like the fact she has twigged her hubbi is up to no good ?
Toxic gossiping nastiness
Not my vibe

Wife is clearly suspicious for good reason, but she has directed it at the wrong person.

He lets it happen because it keeps the spotlight off the person he is cheating with.

I will disagree with the majority of posters.

I don't think it's okay for her to make comments about you and be rude on the assumption that her husband is having an affair with you, considering she doesn't know it for a fact because it's not true. I understand he is cheating on her (or at least he has been for one year out of your 10 year relationship) and that she has suspicions and it probably really sucks to be her. But at the end of the day, that's not your fault and it's rubbish that you're getting all the shit for it.
The husband really should put it all straight. Doubt he will though..