Aliya's body language

Hey guys after watching BI episodes I've noticed one thing about Aliya you see why she's annoyed or angry she does this thing she bites her teeth together. I know it sounds weird but she always does it. You can see her do it in todays scene with Zain e.g when Zain says "Tjum he aachi tarah se pata hai ke tum ne bag ko mall mein chodha nahin"