Aaked to resign under pregnancy period

Hi,
My sister was asked to resign from job saying the project is not renewed and told that she can take rest for the rest of maternity period and will consider taking back once she is back after delivery.
We believe that this is to avoid maternity expenses during the period. She is working in a IT firm in Bangalore.

May I know legality of this and whether we can legally move against the company.

Expecting your expert advice.

Thanking you,
Manu