If the Jeans Fit: Why Blake Lively's 'Sisterhood of the Traveling Pants' Costars Are Still Her BFFs

A lot has changed since 2005, but Blake Lively‘s relationship with her The Sisterhood of the Traveling Pants costars? Steadfast.

The actress tells PEOPLE that she still has a bond with the “incredible” women she worked with on the big-screen adaptation of the beloved book.

“America Ferrara, Amber Tamblyn, Alexis Bledel – those are three women who I met when I was 16 years old and I’ve been lucky to call them my friends and mentors ever since,” Lively shares.

Lively, 28 – who is pregnant with her second child with husband Ryan Reynolds – sees qualities in Ferrara, Tamblyn and Bledel she admires.

For more on Lively, pick up the new issue of PEOPLE, on newsstands Friday

“What they do – whether artistically, politically, socially, personally – they really use their voice,” she says, “and whether people agree with their voice or not is not the thing that I’m most concerned with as much as, it’s nice to see women who are not only empowering themselves but empowering other women to stand up and to really fight and work for what they believe in.”

RELATED VIDEO: Sisterhood of the Traveling Reunions

The foursome reunited onscreen in 2008 for the Sisterhood‘s sequel, and have long teased a third film.

“We love each other, and we love this series, and we are so proud of the work that we did together that it would be wonderful to come back at do another one,” Ferrera told PEOPLE early last year.