Ehrendil could only react at the swinging sword by retreating back, out of its range. He could deflect it but his techniques are all aggressive and the girl would be injured, which is something he isn't brave enough to do.
If she were to be the least bit injured, that's enough reason for her backing to devour his tribe, there is also the option of silencing her so that nobody knows but such a choice isn't a wise one because he was seen by many people when he saw leaving the city in search of Arthur.
"The situation is getting out of hand, don't you think so, Ehrendil?"
Arthur spoke to the distressed Ehrendil, making the latter glare at him angrily and say
"So it's YOU!"
Ehrendil flew straight at Arthur again, intending to finish him but he was interrupted by Jian Si, who blocked his way yet again.
"Miss Jian, I do not want to hurt you, please move away or face the consequences!"
"Hmpf! I'd like to see you try."