Luke
First of all, the betting money on this forum is I am sure that they DID HAVE SEX, probably a lot more than once, so stop praying that you will not be fooled again, because according to what you have written you already believe she is bull shitting you.
Here is what is going to happen. She will tell you that she has ended it, but of course that will be a lie since she has already admitted she is addicted to the excitement of her affair. So it will go further underground.
Workplace affairs are the hardest to catch, the hardest to stop, and the hardest to monitor simply because you most likely will have no way to see what they are doing in interactions 8-10 hours every day, and you will most likely not have any way to access her work e mail or phone at work.
For you to rely on trusting her word is insane at this point. And your chances of stopping this at all if you accept them being friends is non existent.
You should do the following:
(1) don't bluff. See an attorney and get divorce papers drawn up. You can stop that process any time you want to and it does not happen immediately. What it does do is let her know that there are going to be consequences for her actions and that you are not fucking around.
(2) find out who this OM is and tell his spouse if he has one. Do not give your wife notice that you are doing this.
(3) draft a letter to the HR Department of her employment and tell her that if this does not stop immediately you will notify them.
(4) She needs to QUIT that job or begin looking for another one like yesterday.
(5) get a VAR and put it in her car. She will be talking to him in the car where she feels safe from you. Also put a GPS on the car.
(6) do not accept any "girls night out", or week end trips at this time from her. She is probably going to meet him.
(7) if she insists on telling you there was no sex involved, tell her since she has lied already, you will schedule a lie detector test. She will either do one of two things. If she wants to save your marriage, she will readily agree if she has nothing to hide. If she goes ape shit, you have your answer.
(8) you get passwords to ALL social media
(9) she shows you and sends with you no contact communication to OM.
You have a wife who only regrets she got caught, has admitted she likes the attention (which will not change), and is daring you to strap on some balls and do something about it.
You have two distinct choices here
EITHER ACCEPT THE OPEN MARRIAGE THAT YOUR WIFE HAS DECIDED YOU ARE HAVING
FILE FOR DIVORCE AND GIVE HER YOUR DEMANDS, NOT REQUESTS TO STAY MARRIED TO YOU
If you do no more than what you are doing now, yes you will be played for a fool again
ONLY YOU CAN STOP THAT FROM HAPPENING.