She really is an ornery old gal. I took over Sanctuary as my first Vassal, which went pretty well. Carla got excited during the assault and took the raider's side, shooting down settlers. Clearly she could see which was the wind was blowing. All seemed fine. But after returning to Sanctuary after going elsewhere, I was greeted by the sound of gunfire. Carla was still fighting everyone, and since she's essential, she just kept going. The other essentials were fine, but she slowly killed off all the other settlers in the place.