The 20-year-old, one of five Britons in the field, was the only driver to lap inside one minute 39 seconds in the first session and also led the wetter second practice with a time of one minute 56.007.
"Walking up and down the paddock, obviously people were pitching to me 'today that was a bit dominant' but... we're all in the same cars and sharing each others' data and onboards," said Chadwick.
"So especially in the dry it's going to be close... the longer tests we've done, you wouldn't believe how close it gets and that's all because we're all sharing each others' data."
Finland's Emma Kimilainen, 29, was the only other of the 20 on track, two of them reserves, to crack the 1:57 mark with a time of 1:56.081 and indicated she had been playing it strategically to not give away too much.
"In the end I didn't want to push too hard to show my full potential because tomorrow is the day I need to be fast. I lifted quite a lot in the fastest lap in the straight," she said.
Chadwick is one of the fledgling motor racing series' more accomplished and better known racers, in 2015 becoming the first woman to win a British GT championship, in the GT4 category at the wheel of an Aston Martin V8 Vantage.
A British Racing Drivers' Club 'Rising Star', she became the first woman to win a British Formula Three race last year and is also now active in the virtual world as a competitor for an esports team.
Last month she was announced as an Aston Martin factory junior driver and is due to compete in the Nuerburgring 24 Hour race in June.
"I know what I need to do and if I can do that, do what I do in every race weekend preparation-wise, then we'll see how we get on," she said.
W Series racers compete in identical 1.8 litre Formula Three cars with a $1.5 million prize fund for the six race championship.
The series has already gained plenty of interest in both social and mainstream media, with television deals also putting it out to a free-to-air audience in countries like Britain, as a concept aimed at helping women up the motorsport ladder.
The series winner will collect $500,000, with prize money down to 18th place.
Only two women have ever raced in Formula One, considered the pinnacle of motorsport, with Italian Lella Lombardi the last to do so in 1976.
(Reporting by Alan Baldwin, editing by Christian Radnedge)
