Dantewada Assistant Public Prosecutor Rakesh Kumar Singh told PTI over phone that District Judge Anita Dehariya let off Sori and others, who were arrested for the July, 2010 attack on the house of Congress leader Avdesh Gautam.
They were acquitted due to lack of sufficient evidence against them, he said.
Singh said 66 people were named as accused in the Maoist assault on Gautam's house at Kuakonda in Dantewada. Of them, 14, including the teacher, were later arrested.
Sori is currently lodged in Jagdalpur's Central Jail in connection with another case related to her alleged links with Naxals. She is accused of acting as a courier between a private steel company and Maoists.
Sori was named by the state police in nearly half a dozen cases related to Naxal activities and she had been acquitted in some of them.