Frankie Smith was handed an eight-year prison term at Bradford Crown Court in December.
Attorney General Suella Braverman said this was “unduly lenient” and referred the sentence to the Court of Appeal,
Three senior judges considered the case and extended the original term by four years.
During the hearing, Lady Justice Sharp said Smith had a “deliberate disregard” for her daughter’s welfare.
Smith was convicted alongside her partner, Savannah Brockhill, 28, who was jailed for a minimum of 25 years for Star’s murder.