I just wanted to give my thoughts on this, you can do with it what you want, and toss the rest..
This is coming from a separated, middle aged woman who has been in mono relationships all her life...so...you are getting the conventional view, I suppose?
I'm thinking this...the women that are working with your hubby are thinking he's just terrible for hitting on this co-worker, and he's married. Do these people know you have an open marriage? I'm guessing not. Most people don't take that well.
Oh, and I bet a dollar to a donut that they think the GF is a slut of the first order for even hitting on or acknowledging his advances...
I'm sensing that the workplace is female dominate? The profession I work in (health care) is dominated in a BIG way by females. And...we can be CATTY bitches. I'm guessing the one woman is loving this sich unfolding, and she's going to have all kinds of fun sitting in judgment of the hubby and the GF, not understanding the dynamic (or not caring).
Sad, really. Yeah, she, and the rest of the peeps need to mind their own business, but, guess what. They won't.
Dating your co-worker is pretty hard in a mono relationship, let alone a poly one. I'd be hard pressed to ever date a co-worker again. I dated my second husband when were in the same company in the Army, and we saw each other almost ALL the time.
That was really hard. It got a lot easier when he was out, and I soon followed him, and we were at different hospitals....
I don't know if leaving the job (unless there are other reasons for his leaving) would solve the problems in the long run...the short one, perhaps, and the economy being what it is....hell, I'm doing good if I HAVE a job, and forgive me, I wouldn't be giving up a job for a possible boyfriend....unless he's some DAMN fine specimen;0)
I wish I had ideas, I don't. I just wanted to...well, give you a take on how a straight, mono middle age woman might see it??