Advice appreciated

[Btrow]

I'll quote the conversation I had with my XW the day after her 40. birthday party, 4 months before BD.
Me:"why did you sit him at the table next to ours directly facing you when you know I'm not comfortable with him"
Her:"come on, it was a coincidence, he is just a friend"
Me:"I'm really not comfortable with that friendsship"
Her:"how about you and "female coworker" (whom I go to lunch with at Burger King one a month in a group of four and exchanges maybe two texts with per month when gossiping about people from work and other silly stuff), I'm not comfortable with her... "
Me:" come in, its just "female coworker". I don't even consider her female. She's just one of the guys, not even a sexual being in my eyes"
Her:"exactly the same way i feel about OM"

Who is now banging her on a regular basis (I assmume...maybe they are playing bingo every night LOL)

The friend HAS to go....