I thought while watching the Silent one was another person. Fitz wasn't mentionned, although Silent Fitz also is one of her nicknames.
We've not seen Fitz in a laboratory and her mission to protect the princess doesn't match with working in a laboratory for long hours/days.

I'm with Kraco regarding Eris, she is the cause of his disorder and his depression. In that state you try to avoid thinking about that person.