Court documents showed she tore the girl's toe nail off and then poured boiling water on the wound.
The pair were charged after the girl was found in November last year hiding in a cupboard, and reportedly starving, dehydrated and covered in countless injuries.
The charges against the woman include assault on the girl with a machete and hammer, kicking her in the vaginal area while wearing workboots, tearing her toenail off and pouring salt on the bleeding toe, and writing abusive comments on the girl's body.