The 22-year-old actress announced her engagement to singer/songwriter Joe Jonas on social media back in October, where the couple posted matching pictures of their rings, but Sophie is "holding off" buying her wedding dress for their 2019 nuptials because she wants the most fashionable bridal outfit she can find.
She told PeopleStyle: "I think fashion s ever-changing. You never know what's going to be fashionable next year, so I think I am just holding off for now."
Sophie is currently reprising her role as Sansa Stark while filming the eighth and final season of the hit HBO show 'Game of Thrones' which catapulted her to fame.
As a naturally born blonde, Sophie admitted when she dyed her hair red for the show, she felt very insecure and weird.
But as her character - who has survived from season one in the bloody show - transforms from a "young girl to being a powerful woman", the actress started to associate the red hair to "strong women".
She said: "As a redhead, I was originally really shy. I was 13 and changed my hair from blonde to red [for the show] and I was like, 'Oh my God, this is so weird, this is not me.' But my role in 'Game of Thrones' went from being a very vulnerable and insecure young girl to being a powerful woman who is very confident in herself and very empowered. So whenever I think of my red hair, I relate it to such a strong woman."
For the highly anticipated upcoming season, Sophie will be sporting a wig for her role but admitted she hates wearing one as she feels it doesn't like someone "commit to a role".
She said: "It's really empowering thing to use your hair for roles.
"When you're wearing a wig, it gives a sense of momentary transformation and it doesn't let you really commit to a role.
"So I try to really use my own hair."
'Game of Thrones' is slated to return to TV screens in 2019.