1) since your mother has issued blank cheque to money lender and given blank stamp papers the money lender has filled in details and presented the cheques
2) your mother has to contest the case filed by money lender
3) in her defence take the plea that there is material alteration of cheque . date and amount has been filled in by the money lender without her consent
4) make an application that cheques be referred to Central Forensic Science Laboratory ('CFSL') for its opinion on the handwriting on the cheques.