Only you may have a clue as to how she would react to an apology. She might not ever want to discuss the "joke" (that I thought was a riot) but she might want or need you to validate that you had a very Politically Incorrect moment that made her flinch.
Seems to me that even though you don't think you are applying pressure to her, you are from her perspective and she keeps withdrawing from you. You are a pretty intense guy and she just may need for you to mellow out a bit to get herself in a better place before any more action.
It's that old dammed if you do dammed if you don't scenario. I would make a brief apology and drop it entirely. If she wants to talk about it, then do so briefly then drop it.
