Sonnya is the main character of our story, and is a fairly kind, albeit quirky girl. However, she's not afraid to do what she has to in order to get what she wants. When needed, she can fake all sorts of emotions, and use her cute appearance to her advantage. She's also shown to have no problem lying and hiding from her parents. She shares a deep connection with her brother, Milo, which drives her to move forward multiple times within the story. It's also clear that she has some dark past, though she isn't willing to share.

I imagine Sonnya with a fairly young, mid-high range voice. It's also important that you're very expressive, as Sonnya is very vocal with her emotions.