Telling Tonks that her father died and then she died wouldn't have been a smart move. It wasn't that she would react horribly... but she would react badly. There was a difference! Either way, it wasn't a nice thing to hear that she hadn't gotten to raise her son. So she didn't question when Teddy didn't say anything about having already met her because it wasn't strange that he didn't respond to it.
"Or me," she pointed out with a sly grin. "I'm not evil." She followed his gaze to the bedrooms, managing a smile. "You can have the one closest to the kitchen. It'll keep me out of the kitchen for late night snacks." Even in dreamland, Tonks should watch her figure. Or something. Mostly she'd just been told that eating before bed was bad for her. She'd never really listened and she probably wouldn't now, but she could pretend like a good mum.