1.) Stellar wasn't going to survive outside of the Extended program. She needs routine maintenance that only they can provide. I'm inclined to assume by the end of the series, it was logistically impossible to keep her alive.
2.) Shinn wanted to *save* her from war. Joining ZAFT is the exact opposite of that.
You'd think Stella'd have a uniform more like Mu or Murrue's, given she's an EA soldier.
Assuming that she survived her Extended condition and she will be fully freed from that AND still conserving her combat skills, Stella having a Red Compass uniform (not the first time seeing that, post #7645639 also has her with that uniform) is logical given that she will follow Shinn. With that in mind, I see that Stella and Agnes will certainly not get along, constantly bickering a lot and all with the same voice.
I wonder those Japanese medias - the successors of WWII Imperial General Headquarters' announcement ever detailed reported the loses of Ukrainians to let the normal Japanese people know about it.:BlobThinkingGlare: