After losing her humanity, the previous human Queen utterly altered. The death of her kid had devastated her, and she had severed all ties with the Human Race. Nobody expected her to do such a thing, and no one blamed her. Her life was a living horror from start to finish. Her one ray of hope was her son, Cain, whom she had lost in the middle and had not seen for the last time.
Losing a kid was excruciatingly difficult for a mother. This is because every kid that was born from them was utilized as a part of them. The kid grew in them, was nursed by them, shared life and death with them until the infant was born to live its own life. It's a treasure they grew in their bodies and something they're related to via blood. A family, a darling young one. So losing Cain was the same as losing her universe to this Queen.