It was previously reported that Bubba Lewis, Joey Pollari, Zack Pearlman and Mark L. Young will play the four awkward teenagers at the centre of the show.
Deadline now reports that Frnka will play an attractive high school girl who becomes the object of the boys' attentions.
The actress previously appeared alongside former Without a Trace star Eric Close in Lifetime television movie Unanswered Prayers.
Flight of the Conchords director Taika Waititi will helm the pilot, which has been adapted by Brad Copeland. Copeland will also executive produce alongside Damon Beesley and Iain Morris, the creators of the UK original.
Production on the US Inbetweeners pilot is expected to begin on January 10 in Orlando.