The victim's mother cannot withdraw the case already filed and charge sheet submitted to court, the court framed the charges against the accused.
There is no provision per se to withdraw a case under POSCO as these are non compoundable offences. However you can try to get the same quashed by the high court based on settlement.
If high court is not amenable to quash the proceedings then the only option that remains is enter the witness box and deny the veracity of the complaint.
The Delhi High Court held that the court cannot permit quashing of FIR merely on the ground that the parties have entered into a compromise where the FIR relates to heinous offences against small children under sec. 377 of Indian Penal Code and POCSO Act. Justice Subramonium Prasad has dismissed the petition filed under sec. 482 Cr.P.C. praying for quashing of an FIR