Other boyfriends had promised Rose things like that before, but they'd never felt so real. So.. beyond human. There was something about this relationship between the Doctor and her that just felt like they were the only thing in the world.
She'd known that early on--probably the minute she took his hand. She hadn't realized it would be like this. She hadn't realized she was in love with him. But she'd known that what they had was special. That it was more than anything.
She nodded, hugging him tightly. She was safe now.