"So you think we'll get out of this, then?" Since he said that he'd return sooner or later. Tonks believed that they would as well. She was an optimist at heart, really. But it was good to know that other people thought so as well.
She saw Andy as well, and that was part of the reason that she said 'let's go! Never hurt to bother a friendly person, keep them company. But the Doctor must have seen something that she hadn't, because Tonks didn't realise that Andy was sleeping.
Instead, she followed along for the adventure of exploring.."A graveyard?" That was curious. And creepy. "Was this town an actual town before being turned into the ant farm, y'think?"