She may take advantage of your absence in India and may even forge your signature to usurp the money lying in his account.
You can issue a legal notice to the bank in this regard stating that since you are the nominee, the amount lying in the account of the deceased has to be paid to you immediately or else you will drag them to the consumer forum for deficiency in service.
The bank cannot hold the amount in the absence of any court restraining order.
The police cannot instruct the bank to stop the payment just because they received a complaint.
You may approach even civil court seeking direction to the bank to pay the amount to the nominee especially when there is no restrictions for such payment by an order of a court of law.
You can issue a legal notice to the police also to not to interfere in the civil matter because there is no offence committed by anyone hence they do not have any rights to direct the bank authorities to stop the transaction or payment.