No SO for me now, but my late husband was my husband largely because he was loyal, as was I.

Regarding your situation, I would let her know you are not intetested, citing that you like and respect her SO. If she is in a position of power over you, work wise, she is breaking the las (if in the US).

I have a young friend at work who I have no romantic draw to, who recently married and now flirts inappropriately with me. So, in a way, I feel your pain. He has not backed off despite my direct insistence that he do so. It's probably going to cost us the friendship since he wont. Friends don't deliberately make other friends uncomfortable.