OK, I see a couple of troubling signs here:
1. You already feel like she's dismissing any input you have on the matter and plowing ahead with, at the very least, investigating this relationship style that you are simply not interested in.
2. It sounds like you are away from any social safety net you may have had and that isolation is compounding things. To take the least optimistic view of things, it seems like you got caught up in a bait and switch..."Here, let's try out this new location aaaaannnndddd while we're at it, let's bring other people into our relationship."
3. It is to the point where it is affecting your health and, again, she seemingly is not concerned about that at least to the extent that she understands this.
All of this sounds like a big bag of not cool to me. If she wants to hang out with poly people, let her and forge your own path in this new place where you reside. Find your own comfort level with people who share interests. Volunteer somewhere, that's a great way to meet other folks. Join the Y to exercise off some of that anxiety. And, in doing all of this, take some time to establish a few things in your mind:
1. Do you still want to be with this person or has this shift in their desires and personality brought about an end to what you once had?
2. Do you geographically be where you are right now? Or would going back be a better choice?
You're in a tough spot, no doubt. I had something along these lines happen some years back when I rearranged my entire life and moved to be closer to someone who then began wigging out on me inside of a month of our long-distance relationship becoming a short-distance relationship. I worked with him for seven months to see if there was anything worth sticking around for and, during that time, saw my health get worse and worse from stress. Then I just left. Nothing like waking up a few days later in the spare bedroom of my gay ex-boyfriend without a job and without steady income and without much hope of my heart healing but feeling a million times better nonetheless.