Rose heard the snarl in her head get louder as the Master caused the Doctor more pain by punching him on the stomach. She was pretty certain she was falling more and more under the song unable and unwilling to fight it, if it meant that her Doctor would be safe.
Caitlyn bit her lip to stop herself from calling out to Rose to get her to calm down. She wouldn't distract or call attention to Rose that way. It would be up to her to decide what to do, she just hoped it wasn't something that caused catastrophic consequences.