The 29-year-old took one hour and 17 minutes to emerge victorious 6-3 6-3 against the number four seed.
"My goals have been just to give it my all at every match and every tournament," said the 13-time Grand Slam champion after the match.
"Not that it wasn't like that before, but I had a tremendous amount of focus in the grand slams, and I think I still will.
"But every now and then you never know, tomorrow [the final] is not promised and I want to give it my all."
Williams will face tenth seed Samantha Stosur in the final.