Heh. Sometimes I wonder if a gender indicator (gendercator?) would be good on these posts. *sigh* Looks like I need to recalibrate my poly-decoder ring. *click*clicky*click*
The questions remain essentially the same. In some ways, the details you added remind me of any early poly relationship. She and I (I am a dude--in case my charming faux pas didn't make that obvious) are both poly. I have never have jealousy issues--I may not have had that feature installed at the factory. However, she had fits of jealousy. She'd say things would be fine before the fact, but after she would withdraw or get angry. Generally she didn't process how her reactions were sending mixed messages.
Thinking about your situation, it may be more up to Z (N? L? Decoder on the fritz! *whack!* *click*) it may be more up to Z to bridge the divide with Q. She may feel that you are taking away something that's hers. Z might be able to get the message through more easily than you can.
All in all, it sounds like there are three people who care deeply for each other. I hope you find a solution that *clicks*.