Sophie, 22, also added: "I can tell you that there's definitely a coming together of people to fight the impending doom. There's a lot of tension between these little groups, battling for what they think is right."
Despite being sworn to absolute secretly, tidbits of information have crept from Sophie in particular, nodding to exciting plot developments but never giving anything major away, the Daily Mail reports.
She previously revealed that the entire cast "applauded and wept" at the final table read, when they joined for the last time to go through the last script.
As it's the final season, all bets are off during season 8, and Sophie also revealed that her character, Sansa, is embracing her role as a fighter.
"I always saw something of a warrior in Sansa that I don't think other people really saw," she said. "I always had the feeling that she was learning and adapting and at some point or another it was going to manifest itself somehow.
"And she manifested it into being a warrior. It felt really satisfying when it happened, and I'm really happy where this story-line for her has ended up."
It seems that Sophie's scenes have either been wrapped or she's back to wearing a wig on set - as she debuted a stylish new look this week.
The actress has spent years dying her natural blonde hair red for her role as fiery redhead Sansa on the HBO series and, while lately she has been sporting long blonde locks, she's now taken it to a new level with a cut and dye that gives her "Khaleesi blonde" shoulder-length hair.
The British actress, who's engaged to musician Joe Jonas, took to Instagram to show off her new stylish lob and icy blonde waves.
It immediately drew comparisons to the Game Of Thrones character Daenerys Targaryen, who is played by fellow Brit Emilia Clarke.
Sophie is an ambassador for Wella Hair and gave the brand a shoutout in her social media post.
In the seventh season of Game Of Thrones, Sophie wore a wig for her role as Sansa, after previously dying her hair red for filming.
"I started wearing a wig in season seven because I had dyed my hair blonde and it wasn't the best experience, so we couldn't really dye my hair back red," she explained to ELLE.com.
She had to go red again for her role as Jean Grey in X-Men: Dark Phoenix set for release in February 2019.