The court, not your daughter, will decide custody matters based on the best interests of the child. A court hearing will be required. I suggest you hire a lawyer to make the best argument possible.
Your daughter has the ability to give her opinion and requests as to the custody of the child but the Court will make the ultimate decision. If this is the initial custody determination of this child then the "best interest of the child" standard will be applied. Simply meaning that the Court will determine through witnesses and expert, if applicable, who the child should be place with. The best interest of the child standard insures that the child’s "best interests" are taken care of. The Court will inquire into the child’s health, safety, and general moral and social well-being. It is very important that you hire an attorney who is familiar with family law and the area of child custody.