Riding on the sympathy wave, Sowmya, a software engineer, got 99,748 votes, pushing her Congress rival Bodapati Babu Rao to a distant second with 24,921 votes in a straight contest in Krishna district.
The main opposition YSR Congress Party had not fielded candidate after TDP requested other parties to make the election unanimous.
The by-election was necessitated following the vacancy caused by the death of Sowmya's father due to a cardiac arrest days after he was elected in the May polls.