Broody allowing their chick's to get a good solid peck from another chicken isn't necessarily unprotective. My broodies are always fierce the first day or two. After that 'safe' is right near or under her. If the chick invades the others space they get a peck. The chick screams and runs like it's going to die, but the hen pecking doesn't pursue.
My broody never attacked me. Or my dog. I thought much like you she was indifferent. My mom (a stranger to them) came for a visit and wanted to see the chicks. She was flogged for 20 feet and momma hen wouldn't allow her any closer after that.