Why does Emika have difficulty trusting others in the novel, Warcross?

Emika constructed a beautiful yearbook to show her father when she was just eight years old, something that she labored over arduously for days, only to have her father brush it aside because of news from her estranged mother. Emika's yearbook symbolizes the irrevocable damage that her mother has done to Emika. Because Emika's mother left and never spoke to her daughter again, Emika struggles to trust others and work in a team, preferring to work alone and depending on only herself.