It unsettled her to see him this way. He was always the strong one, always holding her up when she fell. No, she hadn't been thrilled to be here, dragged against her will across dimensions (yet again) and time in order to fight for a world that wasn't her own. But she had accepted it. She'd told Anna she would do it, she'd even said she'd have done it if all they'd done was ask. Maybe, in some ways, Davros had been right. Maybe the Doctor had trained a group of fighters. But if becoming a fighter meant she had something to stand for, she wouldn't argue. It's what she wanted to be.
But to see him just give up? Hell, she'd been through a lot, too. Maybe not what he had, but he hadn't seen many of the things she had. When she told Donna and the people of UNIT that she knew what happened when a name was dropped in the wrong place, she hadn't been kidding. She'd been the cause of more than one incident that she had to live with for the rest of her life. She could leave, but the people who lived there were trapped with her mistakes.
Against her better judgment, she reached out, placing her hand on his. He was shaking and she couldn't stand it. The strong, unflappable Time Lord was falling apart. She was still hurt and she was still angry and she could still go for a drink or three to pretend it didn't hurt this way. But she'd be lying if she said she didn't still love him and she couldn't stand to see him in so much pain. "You can do it," she said softly. "If anyone can, it's you. You're not alone here. There's so many people, amazing ones, completely brilliant ones." Fictional ones, but hey, so were they. Oh, he was going to take that well, she knew. "And you were about to regenerate anyway. Now you have more time as you." And more time with her, but she wouldn't say it. Let him come to that conclusion himself. Let him to decide what to do about it. Because she wouldn't. Hell, she couldn't.