She would have smiled to see him so animated, so very him, if not for what he was saying, if not for why he was saying it, if not for the fact that it was nothing to him to... She just stared, her dark eyes far too large for her face now, and made herself face what she'd done. All of this, her fault. She'd messed up before with him. The worst was the reapers when she'd saved her dad from the car -- but that didn't compare to this. At least then, she hadn't known at all what consequences she could bring about. Then, she'd no idea about the laws of time, or how terrible an idea it was to visit her own timeline - twice - to try to be there when her father died.
He'd done that for her, too -- done it without blinking. Just threw a lever and they were off to tear the universe to shreds. All because she'd asked.
But this... She should have known better than to let him go. She should have known that he'd...
"Oh, Doctor," she breathed at last, then started pushing away the books covering his legs. It hurt to see just how thin he was, just how far gone... She should have paid more attention. She should have just gone up to him and asked how he was doing, the last time she saw him at work. She should have made him come home. All of this, all of this was her fault. Rose looked up at the circles on the wall, knew them from the TARDIS displays, and was glad she couldn't read them. Likely whatever he'd written on these walls could burn holes through the universe. Easy.
When she'd cleared the books, she looked back at him. It hurt, it really hurt, to see him like this. She caught his hand in both of hers - and it was cold, far too cold. "It's time to stop now," she said, very gently.