Turner said she was visiting a house in Miami, Fla., with her now-fiance, Joe Jonas, when they were told Bieber was upstairs.
The pair walked up to find Bieber shirtless and getting a head massage.
"I was like, Oh my God, this is amazing," Turner recounted.
"I was like, 'Hi. Nice to meet you. Sophie.' Played it cool. Ran into the closet and, like, cried for five minutes."
"I came out with Joe and Justin goes to Joe, 'Hey, Joe. I heard you got a new girl.' Joe goes, 'Yeah, there she is. She's over there.' I don't know what came over me to do this, but I turned around and was like, 'Hi,'" she added, making a gesture with her fingers and tongue.
FOLLOW REALITY TV WORLD ON THE ALL-NEW GOOGLE NEWS!
Reality TV World is now available on the all-new Google News app and website. Click here to visit our Google News page, and then click FOLLOW to add us as a news source!
Turner is a longtime fan of Bieber who tweeted in 2012, "@justinbieber 'boyfriend is amazing, pretty sure I made up the 8 million views within 24 hours. #proudbelieber."
She told Entertainment Tonight in July 2017 she would love to have Bieber on "Game of Thrones."
"I've been talking about Bieber coming on the show for a while now," the star said.
Turner plays Sansa Stark on "Game of Thrones," which will return for an eight and final season in 2019.
Copyright 2018 United Press International, Inc. (UPI). Any reproduction, republication, redistribution and/or modification of any UPI content is expressly prohibited without UPI's prior written consent.