Heather Fell, who won Olympic silver for Team GB at Beijing 2008, and Katy Burke advanced easily out of their qualification B group in Palm Springs.
With the top 12 from the two qualifying pools progressing and then the next top 12 points scorers, Burke ranked sixth while Fell was two places behind her in eighth.
However it was not such plain sailing for the two other British females on the team as Kate French and World Cup debutant Jo Muir both finished outside the top 12 that automatically qualified.
French placed 15th in qualification group A with Muir 18th. Their scores ranked them in the next 12, though, to ensure Britain would have a full quartet in Saturday's final.
China and Russia are the only other nations with four in the final while Britain's men fell one short of achieving the same feat with Jamie Cooke, Joe Evans and Sam Curry advancing but Tom Toolis missing out.
Pentathlon GB performance director Jan Bartu was satisfied with the outcome.
"It was an exciting day with two very different stories. Heather and Katy sailed through the competition with a good swim, strong fence and combined event, they were never at risk of missing the final," said Bartu.
"The other two girls struggled from the outset in the fencing discipline but fought back in the swim and combined event.
"It's fantastic news that they all made the finals and it's especially encouraging for the younger athletes. I'm really pleased they have another opportunity to compete at a world-class level and gain such valuable experience."