I had one “Bergamot” who got really aggressive with the other girls, I separated her for a day, that did nothing.
I separated her for another day then introduced her back to the flock with a piece of white cord very loosely looped around her neck, there really wasn’t much keeping it on besides her feathers.
She was still aggressive towards her flock sisters but every time she moved she saw the string move which spooked her, she spent more time being spooked and distracted by the string than she was focusing on the other quail.
After around a day and a half she relaxed and her ire disappeared. She also managed to get the string off but I think it did its job. It was definitely very stressful for her but it may have trained her to have a negative association through a fear response every time she tried to attack the other quail, or it was just enough of a distraction while she worked out her issues.
Whatever it was I didn’t have to cull her and there’s been peace in her flock since.