The Doctor gave Rose a good look over to make sure he wasn't missing anything before accepting what she told him at face value. When she asked about the TARDIS the corner of his mouth twitched slightly before he spoke.
"She's fine."
He knew he could do a much better job of lying to Rose if he wanted to but he didn't have it in him. The Doctor wasn't prepared to admit how bad it might be.
Case in point, they were towing The TARDIS to the new location instead of simply going there and letting everyone else catch up.