Dear Gaurav,
The minimum qualifying continuous service of 80 days has to be calculated backwards from the expected date of delivery only. Please note that the 80 days need not spread across the entire 12 months period so as to construe a continued employment during the 12 months period.
Including the date of intimation about her pregnancy, the employee has already completed more than 80 days of service in the establishment.
Therefore, no doubt about her eligibility to avail the statutory maternity benefits thereafter.
In this connection, you may please refer to sec. 5(2) of the Maternity Benefit Act, 1961.