The girl is seeking asylum in your house, she is a major by age. So she is entitled to stay in your house as long as she wants.
For this she has to lodge a complaint within the jurisdiction of where your house is located, stating the true facts about her marriage, torture in the hands of her husband and in-laws, and fear for her life from her own parents who might force her to go back with her husband and in laws. This should protect you from any kind of false complaints that might be lodged by her husband or inlaws including her own parents. She must categorically state that she is filing this complaint voluntarily and that she fears for her own safety, and the safety of you both who is now protecting her against the ill-treatment being meted out by her parents and in-laws.