You can also let them break on own as long as they are fine.
https://timbercreekfarmer.com/10-signs-you-have-a-broody-hen/
Interesting link. I've seen practically all those with hens that were not close to being broody. Maybe that should be titled signs you might possibly have a broody. And they missed my main sign. If the hen sleeps on the nest for two consecutive nights instead of in her regular roosting spot she is broody enough to deserve eggs.
I've seen hens do things like walk around fluffed up and clucking when off the nest, defend their nest when they are only laying an egg, even spend one night on the nest and never go broody or flip over to full broody. So if they are doing some of the things that a broody regularly does they might be thinking about it, but most of the time there is no warning. They just flip from not broody to full-on broody.
Dona, just because a hen goes broody does not mean you have to give her eggs or chicks. When I have a broody when I don't want more chicks I use the wire bottomed cage method to break her from going broody. That is in your control, not the hen's.
You said she is the dominant hen, I don't know if you have a fully mature rooster. Sometimes a dominant rooster will help take care of chicks since they are part of his flock. I don't know why she behaved that way but I'd think it much more likely she was making sure all of her flock was OK instead of potential broody behavior.