Bluegoldtiger came back. I helped her out a little with setting up her new territory, far, far to the south (she found an island and started setting up, I gave her some items and helped a little with construction).
After I signed out, she backtracked all the way back to my territory and griefed it. I can 100% confirm it was her because I'd just been there prior to signing out, nobody else had logged onto the server, and her current position (saved in her player data) shows her in my territory again.
So, I've banned her. If there are any objections, let me know, but I'm done with her being here, personally. Petty.
I've also seen minor damage she's caused on Nibiru, but I'm less concerned with that because Nibiru is modded and it's easier to fix.