Hideaway Strath I know your style

I cackled at Alduin omg XD

She chuckles softly at the awed look upon Alduin's face the decision he seemed to make that he likes her, then as he tries to take a dominant stance and look fierce, she can only smile wider as he hops forth and continues to try and both look and sound mighty. 
Child as he was, Nyra got a wicked glint of her own in her eyes, and took her own rigid, dominant stance, letting out a loud, guttural growl. However, she didn't bare her teeth at him. Her display was meant to spook, awe, and rile, therefore not an intentional promise of harm.

In summary, she was showing off a little bit.