Legal Question in Mediation in Maryland

It would be helpful to have more facts before answering your question. You write that your former mother-in-law wants your daughter to "come back," which suggests that your daughter lived with her grand-mother, either informally or under some agreement or court order. Is there a custody order? A legal parent has substantial advantage over a non-parent in a custody dispute, but that advantage may not exist if the third party has a custody order, or if the legal parent is unfit, or if exceptional circumstances exist.