Thanks for your input Sage. We definitely need to learn to communicate more openly and effectively and we are on that path. My concern is that my negative thoughts about Poly will sabotage our relationship before we learn to communicate and work through it.
I'm sorry that I can't completely relate to where you are coming from, but I'm a very empathic person, so to an extent, I can.
Your negative feelings about poly need to be honored, just as her desire to explore the relationship needs to be. I can only speak for myself, but things improved significantly when DW started saying how he was really feeling, because then we could address it. Does that make sense? For example, he thought that my loving another represented some inadequacy on his part and that simply isn't the case. Since he's been more open, we've tackled a lot of monsters that needed to be tamed. I think it's important for you to make it clear to her how much you want to be okay with this, but that it will take you time. That's very reasonable! Maybe others have said the same, but I haven't had a chance to read through the whole thread.
Jealousy is a feeling you are feeling and it tells you something. A friend of mine had a nice re-frame of this when he said that jealousy indicates how much you value the other person. The trick is to look at what it is trying to tell you. What I "hear" you saying is that you are afraid of losing what you have. Who wouldn't be when a significant change like this occurs?
I wish you much peace and love through this journey!