You are right, BU, that I should NOT talk to Danny first. I actually realized that myself last night when I was talking to him on the phone. Jean has been sick, and he was asking about her, how she was, etc (of course she was working so he couldn't call her himself) and I realized how much he does care about her and how immoral and unloyal it would make me look in his eyes to even bring this up to him. It might end up pushing the two of them together and leaving me out in the cold.
Also - I can see how your point about the hormone rush that comes with a new relationship can be threatening to the existing relationship. Because I do get butterflies when I talk to him or am around him, and I could see how, especially sexually, that I would prefer him to her and would want to be around him all the time, making Jean feel left out and jealous.
How are we now? Well, let's see, we are close, we talk about most things, definately have friends in common. Sexual intimacy is lacking because we have very different work schedules, bedtimes, etc. so there is not alot of opportunity. I enjoy flirting and touching Danny, in fact recently Jean commented on that saying it was "weird and obvious that I want to rub on him" (i.e. I gave him a massage because he was in pain, and then a few days later offered to do another one). So I realized I need to reign myself in a little in that regard.
I think I may just say to her that it is OK with me if she wants to date Danny, and see how she reacts. At the very least, it will open up the discussion.