Because she refused to back down on immediately slaughtering him without even letting them try to get him out of the armor and immediately went on the attack. It's 100% the elf's fault.
Yeah, that's why I really can't get behind our party here. As said, assuming they get out the fallen can be brought back. But if they don't defeat the demon snake, they all die on the spot and nobody will save them. At this point the party is that sort of bystander that causes extra risk and obstruction during a police or rescue operation.