Yup, now Caitlyn knew she couldn't keep her mouth shut here. "The good of the many outweighs the good of the few. I don't suppose I have to ask what you would have done. You ran and somehow found your way to Earth. So what exactly does that make you?" Caitlyn asked coming to the Doctor's defense. He was important to Rose and so he was important to her, and she stood for her friends. 

Well good things often came to an end. Rose was just impressed Cat had held her tongue for so long. But if Cat hadn't said anything [I]SHE[/I] would have. The Master had no right to point fingers about Gallifrey falling. The Doctor had no other choice if he wanted to save the universe.