One of the staff...a putrid rust-eaten robot.

[Meaning she had far less remorse ending its miserable life than if it were a human. Perona's not a perfect human being, and her hands are nowhere near clean, but killing off a human is admittedly more difficult. She needs a good reason (and one hell of a grudge) to do that much damage.]

If you come across one, I suggest beating it before it gets a chance to get to you.