Nightbane would slice through Zekara and she would die but not before lodging her axe in Emma's chest or neck. It would then be a Claire-Cataclysm screamfest.

Angels are naturally very loyal and very protective, and they are trained from the moment they're able to comprehend to obey the Archangel because they (supposedly) know best. It's why angels are so deep-rooted in tradition- the traditions were created by PREVIOUS Archangels, so they must be the right way to do things.