The 23-year-old Swedish sprinter became the first woman to swim under 52 seconds last Sunday during a powerful first leg in the 4x100m freestyle.
In the semi-finals, Sjöström was the fastest of a powerful field, clocking 52.44 secs, and having bettered her time from the heats, she can go faster still.
"I'm really happy that I went half a second faster, even though it was the same effort for me," she said.
"It was very good, but it will be a very tight race tomorrow."
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Sjöström is predicting a tight battle – similar to last year's Olympic final when Simone Manuel of the USA and Canada's Penny Oleksiak, 17, who are both into the Budapest final, shared the gold.
Defending champion Bronte Campbell of Australia and 2012 Olympic champion Ranomi Kromowidjojo also went through with quick times.
"Just remember though what happened in the Olympics, I'm looking forward to it but it can go either way," added Sjöström.