Tuyen is the youngest of the group, only being 18 years old. She thinks she's smarter and better than everyone when really she's very socially unaware and often comes off as awkward anyway. Think Rachel Berry from Glee. She marches to the beat of her own drum because she thinks she's always right, and she genuinely is very smart having graduated high school early, but she's not all there when it comes to social interactions. 

I don't know exactly how I want her voice to sound so you can take free range with this, but I do know I want her to speak very "know it all" type of way.