Reese Witherspoon arrives at the Oscars on February 24, 2013. Credit: Jason Merritt/Getty

When the time comes to get dressed for high-profile events, Reese Witherspoon seeks the advice of her most-trusted critic: Ava Phillippe! During a red carpet interview with ABC's Lara Spencer on Sunday, Feb. 24, the Mud actress credited her firstborn with selecting her cobalt blue Louis Vuitton gown for the Oscars.

"I was so excited. I saw this dress and loved the color, so here it is!" Witherspoon said. "I love to play dress-up and look at all the gowns."

Witherspoon got the thumbs-up from Ava before hitting the show with husband Jim Toth. "She tells me what's cool, what doesn't look good, so it's fun," said the actress, also mom to Deacon Phillippe, 9, and Tennessee Toth, 5 months. "We get to do it together."

In an interview with E! News' Giuliana Rancic, Witherspoon added, "My daughter and I picked it out. She said, 'This is a winner.' She's 13, so she definitely weighs in. She helps me pick the jewelry, makeup and everything."

Witherspoon -- who won her first Oscar for Walk the Line in 2005 -- added that she was rooting for Naomi Watts, who was vying for the Best Actress in a Leading Role title against Jessica Chastain (Zero Dark Thirty), Jennifer Lawrence (Silver Linings Playbook), Emmanuelle Riva (Amour) and Quvenzhane Wallis (Beasts of the Southern Wild). Lawrence, 22, nabbed the honor.

"I wrote her a letter about her performance in The Impossible," Witherspoon said of Watts, 44. "I just think it was extraordinary. Not since Meryl Streep in Sophie's Choice have I seen a performance like that."