@ruzand - terrifyingly awesome, shes a classy "ride or die" girl. She knows how to read the mood and has top political skills - she will never dip into yandere, shes too "adjusted" for that.
@Yatty12453 - she would need a combination of social alienation, abuse and prolonged or extreme emotional trauma. Dad being busy when you plan to ask him out for an unscheduled picnic, and instead of asking - you give him the cookies while hes working is hardly considered anything major. It highlights her empathy skills - but deepens her alienation - yet its self imposed. She was always empowered to press the issue or stay with father in the study for a much needed tea and cookies break. A compromise that meets her emotional needs without delaying her fathers work.
The key here is our character is empowered and capable of solving her issues through means other than violence. Yandere's typically resort to violence due to the inability to satisfy emotional needs through healthy or productive means while at the same time having a lose grip on their sense of self. Having little notion of your own existence can lead you to shameless and destructive behavior with little remorse - the only thing that matters is your unfulfilled needs you are a hollow existence and your actions have no consequences for every moment of life without your needs is death. Emotional "starvation" where you will eat "dirt" "bugs" "trash" "anything" - such a state will require decades. this character is a child only truly aware of the world 2-3 years ago - barely off the breast of her mother. 2% on the potential yandere meter - something absolutely horrible would have to happen for her to go postal.