Very sorry you lost her.
:hugs
It is always best to keep the broody and her chicks separate from the flock for a few weeks until the chicks are big and fast enough to get away from nasty flock mates.
Poor thing!
She needs some water with electrolytes and vitamins to balance the blood loss and treat the shock.
Inspect your coop closely: can you see some wire or screws sticking out where a chick could have gotten caught or are there openings that would allow rodents to get to the chicks at...