What are good godly ways to deal with a difficult supervisor at work?

What an admirable question! It is rare to find someone so humble who wants to be peaceful. It is so easy to want to be vindictive and retaliate, but I think you are a very admirable person for trying to be spiritual in this pursuit. I am dealing with a similar situation. Every work place has one person like that. In my experience, I find that reading bible scriptures and prayer to be very comforting. A word spoken in kindness can turn away anger. I understand that it is very difficult and that you do not want to be friends, but at some point in time compliment her on something. People such as your boss are typically very egotistical and feel the need to impugn people that work for them. I recommend sending a card and small gift to your employer thanking them for hiring you, list steps of how the job has improved your well-being, and how you enjoy working for that company( even though you don't). It will stroke your boss's ego, as well as make you look really good. You both come out on top, and you will definitely stand out in a good way from other employees. I'm sure you already do.Good luck!