As predicted, a door has closed in the ever-changing world of my polyamorous life. The way with relationships is that they're fluid. It seems to be that when one starts another ends - or vice versa - and anyone in a poly relationship has to truly come to gripes with the fact that this will happen if you don't have a solid relationship (meaning a long-term one).
Jenna has decided - quite understandably - to pursue a more serious, monogamous relationship, having realized that poly wasn't for her. The discussion was short, and I was sad that she thought not only that I would be mad at her for the decision but that I would want to terminate the relationship entirely because of it. For the brief time that she and I were together (with or without Elle), there was very little time spent together, which wasn't really for lack of trying. We both had rather erratic schedules making it difficult to get together on more than a number of occasions. It certainly didn't make it easy to have a sustainable relationship of any sort of healthiness. So I completely understand the decision, and I respect it whole-heartedly.
So I move on from one phase to another. I am grateful for the experience and for the new friend, because Jenna is a wonderful woman, and I truly am happy to have her in my life. I hope, too, that I have brought to her some new perspective on how I live my life. To her, much love.