As a pretext, I'm non Muslim so I will not say anything in relation to your religion, but I'll come purely from my personal moral compass / how I think a human should behave:
This looks all cute and innocent at start...
"Continue being friends"
" I aware I'm being very selfish...."

Oh wait nvm, funny she wrote "what I'm feeling isn't purely lust for you (would be much easier if it was)". This is a big red flag. So it's okay for her to fuck around as someone's wife? I cannot imagine any husband agreeing to that lol. She WANTS to cheat both emotionally and physically...

"Of course there's sexual tension but we never let that lead the conversation ."
...except, she ALREADY crossed the line with her text below.
... But this here confirms to me that she is not doing her role as a wife/committed partner and she's telling her story in a way that benefits her.

In any relationship, if there's a problem, it is often** two-way.
(**exception: domestic violence or abusive relationship)

What has she done for the husband so far? It's easy to take your partner for granted as time passes and/or when you're really preoccupied with your own life -- her having a job. I'm not saying she should quit her job, but I think she's taking the easy way out by looking for a quick romantic connection outside her committed relationship. I believe in fixing a relationship with your partner first, and that includes keeping the problems private so you create a safe bubble for the relationship without external judgement. That means, you as the third party should have never heard anything bad about her husband.

Now, she's definitely part of the problem especially for the fact she said such irresponsible lewd things to a coworker. No sane platonic friend of the opposite sex would describe his/her sex activities this vividly to the other. She's obviously luring you in to cross the line with her.

We do not know the husband enough to pass judgement that he is or isn't doing his role as a husband, but her actions so far tells me SHE is not.

My advice: no.

---Edit:

Lol are you for real?

I guess I should've heeded /k advice, mmg resident troll ni haih

Im not trolling

I have girls around because Im single and available. Im not the one cheating.

They know Im a low hanging fruit. I am approachable, easy to talk to and girls dont see me as a threat because I have what they call “lepat pisang” face.