Congress veteran Vidya Stokes won Theog seat with a margin of 4,276 votes over her nearest rival Rakesh Verma of the BJP.
"This was probably my last election. I am grateful to the people for reposing faith in me," Ms Stokes told IANS over phone from her constituency.
Election officials said Stokes polled 21,478 votes whereas the BJP's candidate got 17,202 votes.
Ms Stokes, a long-time Indian hockey administrator and the daughter-in-law of an American missionary, said: "I am a loyal Congress worker. I have never demanded any post from the party. Whatever the party offered me, I accepted it with grace."
Ms Stokes, who is known for her proximity to the Gandhi family, left it to the party high command to decide who will be the chief minister. She said: "This is for the party high command to decide."