I enjoyed your use of vocabulary. Impressive. Regarding your situation, you may only need a short-term fix since your co-worker is treading on very dangerous ground by dating your boss. My guess is that others in the office have a problem with that as well. Rarely do I see those type of situations play out well in the long run.

Your first responsibility in this situation is to your relationship with the co-worker in question. By that I mean that you have an obligation to address your concerns with her directly. This would let her know that you will assert yourself if need be and hold her accountable for her part in your working relationship. You also don’t want to lower yourself to her level of communication. In other words, don’t give her any material that she can use against you with you-know-who. I think you can be very innocent and subtle in your approach. Something as simple as, “Is there something I’m doing that is bothering you?” can do wonders and it is easy to say. A question like this opens the door and, instead of an attack, it put the onus on her to give you feedback. Keep in mind that there might in fact be something you are doing that is sparking the dynamics. If that is the case, listen to the feedback and merely thank her for it (since you asked). Then you can consider later if it is feedback that your can agree with or not.

Addressing the dynamics between the two of you is the most effective approach for the reasons already stated above. If you don’t do that, you pretty much reinforce the current dynamics because saying nothing is essentially an endorsement of the status quo. That’s my two cents for now. You are the new guy so tread lightly.