I would love such sister. Well, except for youma and all.
The power gap between humans and (half)youma sure is wide. But this particular youma is even more powerful than those before it.
Clare moves to defend soldiers and takes the punch. But if she falls, they are dead meat anyway and mission is failed. So there is more to it than efficiency. Protecting humans at all cost? Maybe those soldiers on the scene can be of some help if orgaized with Claire's pursuers and aware of youma.