Ryan Reynolds is his wife's no. 1 fan.

On Tuesday, Aug. 6, the actor was on hand at New York City's AMC Lincoln Square to celebrate the premiere of Blake Lively's new movie, It Ends with Us.

Lively exclusively tells PEOPLE that "it's the best" to have Reynolds, 47, by her side. She also speaks about her character Lily Bloom's character arc and the support Lily receives from her loved ones throughout the film. "This movie is a movie about a woman who experiences every color of human emotion and the people who love her and support her along the way," she says before noting that she is "so grateful" to feel those supportive sentiments at the premiere.

At the event, Lively, 36 paid homage to Britney Spears by wearing a vintage Versace gown the "Gimme More" singer originally wore in 2002. She also exclusively confirms with PEOPLE the dress is the "actual" gown Spears wore over 20 years ago. Meanwhile, Reynolds sported an olive green suit with a white floral boutonniere — another nod to Lively's character, who works as a florist.

Along with Reynolds, Lively was joined by her costars Justin Baldoni, Brandon Sklenar, Jenny Slate, Hasan Minhaj, Isabela Ferrer, and Alex Neustaedter, as well as Colleen Hoover, who wrote the bestselling 2016 novel that the film was adapted from. Additionally, Reynolds' Deadpool & Wolverine costar Hugh Jackman supported Lively's latest film.

Reynold's attendance at the premiere follows Lively's similar support of her husband at the New York City premiere of Deadpool & Wolverine in July. Lively jokingly told PEOPLE on the July 22 red carpet that her husband was "supporting her" versus the other way around.

"I feel like he's my plus one. That's the energy I'm giving," she said. "He's here supporting me, and I'm very grateful for his support tonight."

Lively's sister Robyn and three of her kids were also on hand at the Deadpool & Wolverine premiere to further support Reynolds and Jackman's movie.