Part of her characterization, I guess.

I guess she was born that way and it's part of who she is

Not much to smile about when your family and your people are massacred and you’re taken in and further traumatized by the person who did said massacring.

You were be angry too if the person that Massacred your people and birth family was the man that you sees as your father and Most of your "Siblings" Hates your freaking guts other then the Robot Girl who you sees get Massacring by your said Father only cause you beat her in everything.