The flock master's work is never done!!!!!My RSLs are meanies and I can foresee them behaving the same as yours did when a broody with chicks returns to the flock. There's nothing peaceful about them, unlike the rest of the flock and they don't coexist well with anyone but each other. Ichabod had to work at putting them in their place and often times would just stand on them to reiterate that he's not going to tolerate their bullying anymore. They treated him far worse than anyone when he joined the flock and they're the only ones I've seen him stand on like that.
When I started raising chickens, I never intended on keeping a rooster and having chicks to hatch so my coop is not designed with proper accommodations. I've been unhappy with it for a while even without having a rooster and future offspring from my existing flock. I am continuously reworking my design for a new one and definitely need to include space within it for broodies.