Asha Devi, mother of ‘Nirbhaya,' on Saturday called for the resignation of Mamata Banerjee, saying that the West Bengal chief minister had ‘failed to handle the situation.’ Asha Devi She was speaking to PTI over the rape and murder case of a trainee doctor at Kolkata's RG Kar Medical College and Hospital. Also, Nirbhaya's mother claimed that the West Bengal …