I've only written with Sera personally once, and that was on Kashyyyk which seems like forever ago, but it was great. PvP with you was awesome and fairly balanced, and having only found a handful of people I enjoy it with, that says something. I have a feeling if the two of them happened upon each other even after the time that's passed it'd still end up being a fight, which would be interesting to test sometime. Something tells me neither of them are the greatest at making friends.
Now, I've only been in a single thread with Jamie thus far as well, but at this point that doesn't matter.
I can see her growing to be just as developed as Sera, even if she does have a lot to learn along the way. Everything about her is portrayed perfectly, and none of it feels forced. She acts just as genuinely as one would expect any teenager to given the scenario, and her reactions to everything being presented to her are spot on. I've always loved your writing, so keep being awesome.