[MamaS]

Sometimes the choice isn't all theirs. I knew a family where the woman surrendered two girls, kept a boy, surrendered another girl, and kept a second boy. It was not lack of love, but lack of financial support. The father of the children (not her husband, but a permanent relationship) said he would only stay with her if she gave him sons. He would not pay anything for girls. She placed her daughters with family members so she could know they were okay, but He did not permit her to visit them.
So maybe she is not "psycho" as Aussie-Chris suggests. Maybe she was financially dependent and emotionally beaten down. You won't know until you ask.