The convicted former cop was seen sitting in the front row and left soon after the flag-hoisting ceremony that was held.
Ruchika's friend Aradhana Gupta said she was deeply saddened to know that Rathore was allowed at the stage during the Republic Day event.
"I am deeply saddened (to know that). The administration needs to give an explanation about who invited him. No girl can feel secure with such behavior of administration," she said.
Rathore, who retired in 2002, was serving as an IGP when he molested Ruchika, a budding tennis player, in 1990.
Ruchika, 14, committed suicide three years after the molestation as Rathore allegedly used illegal means to harass her family and got her brother arrested in a false car theft case.
After she and her friends complained to the Haryana government, Rathore allegedly harassed and tortured her, her brother and the rest of her family, misusing his position as a senior police officer.
Ruchika, unable to cope with the harassment of her family, committed suicide three years later by consuming poison.