@ooPh9quu
I believe it means "someone with a mask can be replaced by anyone" since no one knows her face. Since she isn't "reliable" she can't show her face so that her "master" can easily replace her with someone else. Her "master" can just pick another woman to don on the name of "Raven" if she loses her reputation once.
Even those idiot nobles can tell that 'Raven' is an alias.
Whereas, if she is a reliable person. She can easily show her face, and people will start to recognize her by her visage without her even introducing herself.
I believe she was going for this angle.