Dear Manoj_cil,
You have not provided information about whether you are in HR; however, from your profile, it is evident that you are in a PSU.
PSU HR Policies
All major PSUs, especially the Maharatnas, Navratnas, and others, have a history of well-laid-out employee-friendly Personnel/HR policies wherein such contingencies are also covered.
Since the concerned employee is a PSU employee, I suggest she contact her Personnel/HR officer. During maternity leave, an employee is not required to attend her performance appraisal meeting or perform any other official duties.
I am sure the Personnel/HR officer or their senior will explain to her the modus operandi in such cases. Be assured that PSUs are always compliant with labor legislations and other requirements. Moreover, they willfully extend the coverage of benefits to executives and managers too.
So, there is no cause for any worry that a woman availing her maternity leave will be denied the benefit of promotions whenever it is due.
Warm regards.