Czech Kvitova missed out on a place in the WTA Finals, but the two-time Wimbledon champion has hit form at the end of the year and is on the brink of a second title in the space of a month.
The world number 11 won her only tournament of 2016 in Wuhan three weeks ago and can lift another trophy this weekend if she sees off Niculescu after defeating qualifier Davis 7-5 6-3.
Kvitova came from behind in both sets against the American outsider, who faltered when serving for the opening set at 5-4 up and also lost her next service game as the top speed won three games in a row.
Davis led 3-1 in the second, but again Kvitova came roaring back and wrapped up the victory in an hour and 48 minutes.
Niculescu was gifted a walkover at the quarter-final stage after Caroline Wozniacki withdrew due to illness and the unseeded Romanian dumped out Kiki Bertens with a 6-3 6-3 success on Friday.
Chasing her first WTA singles title since September 2014, the 51-ranked Niculescu broke three times in each set to reach her second final in just over a month – with her previous showpiece appearance ending in defeat against Lara Arruabarrena at the Korea Open.