I don't know. I just really enjoyed the story. Aeryn grew up a soldier and finally learned what it was really like to love. Then she lost that love and went into a deep depression. I don't think it was contrived for that to happen. In the end, however, she knew she couldn't just go on living like that, so she retreated (or tried to, for the next couple episodes) back into her soldier role.
I also liked how Stark was hearing Zhaan and then went off to find her, and had there been a Season 5, I bet we would have learned more about that. As it is, I enjoy the mystery.
Plus there was that really neat baby puppet thing.