One line that really bugged me

Okay, this script was awful and had so many story, character, and continuity issues that I have no idea why HBO thought it was good enough to greenlight.

That being said, out of all the lines that were either stupid as hell or pointless, and there were many such as the famous "I'm gonna make you lick each other's *beep* or the completely hideous "FIE!", there was one that bugged me the most which was when Fiona says to William:

"I know who you are Charles"

It bugged me cause this line and the way she said it acts like she knows William is a con man and lying to her, but later when he tells her she seems completely blindsided and had no idea. This line just seemed utterly useless and confusing. I mean yes, the entire story, if you could call it that, was quite pointless, but this line just seemed completely random as it was never brought up again what she meant by that, since cleary she did not know Charles was actually named William.