The actress also opened up about her wine-filled nights with Meryl Streep.
Reese Witherspoon hit the red carpet with her look-alike daughter, Ava Phillippe, on Wednesday night.
The mother-daughter duo attended the premiere of season two of Witherspoon's HBO series, Big Little Lies. But could 19-year-old Ava appear on the series in a possible season three?
"Oh! I didn't know there was a Big Little Lies season three!" Witherspoon joked to ET on the red carpet.
"I don't know [if it could happen]," she added. "I never say never. You don't know. And [season two] was a surprise."
Season one of BLL ended with the Monterey Five -- Witherspoon, Nicole Kidman, Zoë Kravitz, Laura Dern and Shailene Woodley -- throwing Kidman's character's abusive husband, played by Alexander Skarsgard, down a staircase, killing him.
"I need to take a deep breath every time I talk to her," Witherspoon said of working with Streep. "It was intimidating, for sure."
"I had to sometimes pull myself back and take a deep breath and go, 'OK, she's just a person. She's just a human being.' But it was a thrill. And to get to sit with her and talk about the script and work through scenes, it was just like, 'Are you kidding me?'" she continued. "As an actor, all my life worshipping her work, and she's just as truthful and honest and genuine and fun-loving as you can imagine."
"With Meryl's character coming to town, there's just a lot of tension in Monterrey," Witherspoon teased. But the same wasn't true on the set.
The show's cast welcomed Streep with a glass (or two) of wine. "We like our wine in Monterrey," Witherspoon confirmed with a laugh. "We have some really good wine there, and pizza. We had pizza and pasta and talked about our lives. It was really fun."
"[Working with her was] sublime. Just sublime," she shared.
Season two of Big Little Lies premieres June 9 on HBO.
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