Sherin went missing on October 7, 2017, after her father allegedly put her outside their home at 3 am in Richardson, Texas because she would not drink her milk. Her badly decomposed body was found 15 days later in a culvert near the family's home.
Sherin, who went missing on October 7 from her suburban Dallas home, was found dead in a culvert on October 22.
"After baby Saraswati @ Sherin Mathews' case, have requested minister for women and child development for a thorough investigation into the adoption process," External Affairs Minister Sushma Swaraj tweeted on Friday.
Sherin Mathew left her hometown in Bihar in late 2015 for a new home in America.
The lawyers write that Mathews is "trying to grieve for her lost daughter while still caring for her remaining daughter.
She was 'interrogated for hours by several officers with no attorney present' a few days later.
Mathews had previously claimed that Sherin went missing after he sent her outside their home at around 3 am on October 7 as punishment for not drinking her milk.
Sherin went missing from her home in Richardson on October 7 and her body was found on October 22 in a culvert in suburban Dallas by a cadaver dog after an intense search. The toddler's body was identified days later using her dental records.
The body was found about half a mile from Mathews' house.
Sherin, reported missing on October 7, was found dead in the culvert under a road about 1 kilometre from her home in suburban Dallas on October 22.
The 35-year-old mother, an Indian-American registered nurse, was arrested on Thursday after her attorney took her to the Richardson police station.
Sherin was confirmed dead by US police on Tuesday after over two weeks of investigation. She was missing since October 7.