Tyrhallan noticed the swing coming in, ducking under it and sidestepping off to the rightside. The blow that she intended for him with her rightarm was launched but became aimless. He managed to avoid it by using his own left arm. Bringing it in between her and him and making it act as a lever to push the offensive move to the side, it was only thanks to Tyrhallan's incredible speed that he managed to pull that one off and perhaps also because of the suckerpunches he had ordered his teachers to hit him with. 
He wasn't a romantic fool, whilst he might be an honourable knight, the world was made up of all kinds. He would certainly encounter all manner of spineless gorms. Those with a measure of sense and honour would be rare finds indeed, however it should not sway one from doing one's duty.
She was the enemy, plain and simple. If the forces she had joined not crossed their border, they wouldn't be fighting. 
He had avoided her grapple and spoke in almost a whisper making sure she heard him and he would have her attention again.
"Run." 
He swung his right arm back and brought it down hilt and pommel first as his left hand made a grab for her armour, intending to pull her in for a blow to the head.
He needed her out of commission and fast, she was a timewaster. As much protection as her helmet normally gave her, the blow might be enough to make her unstable. 
He hoped it would be enough to discourage her in continuing to fight him, though he didn't believe it would, it was worth a try.