Melisandre watched carefully employing all of her senses to read Diomed's every move and prepare for his attack.
He had chosen to charge straight at her, and she could see he had his glaive gripped with both hands and trailing behind his body.
From that position it was fairly obvious he was preparing for a big swing from close range that Melisandre could not avoid.
Currently her body was in her owl form, and she was a massive target.
The size she was using to control the area now seemed to be a detriment in the face of Diomed's space severing attack she had no means to block. Her only recourse was to dodge, but that would be impossible for her giant body. Or so it appeared.
'He is clearly not used to fighting beasts like me.'
Once Diomed had initiated his attack, Melisandre watched the line of light come out of his swinging glaive.