I am getting the feeling that Nalani’s father had a romantic relationship with Nancy. Maybe she thought they would get married so when her husband was deported she let him take their baby because she wanted to be “free” for Nalani’s father. (Wasn’t that Susan Smith’s motive and Chris Watts motive?)
However, Nalani’s dad ended the relationship. He called her for a ride as a favor. She felt he was using her and became angry. She reacted by harming Nalani as revenge.
I was hoping she would be found safe, unharmed but based on her arrest and LE search locations, I think this may have happened.