McGarty: 'EastEnders Xmas is fantastic
Shona's character Whitney Dean joins the Brannings' festive celebrations on December 25, which are set to get explosive when Max's mysterious secret is revealed as he prepares to marry Tanya again.
Asked how she felt when she read the script, the actress told Take It Easy: "Really shocked. It's fantastic though, and the outcome is going to shock the audience. There's going to be huge consequences to what happens on the day."
Shona added: "It was brilliant to watch Jo Joyner and Jake Wood do their scenes - they're just fantastic. I enjoyed the whole thing and there's a very exciting build-up. There are 18 people sitting at the dinner table, so you can imagine the drama!"
The 21-year-old also revealed she's uncertain about Whitney's relationship with Tyler Moon.
"It's a bit awkward at the moment for her because she doesn't know what she wants. She wants to be happy and find 'the one', but I think she may still be looking."
The hour-long EastEnders special will be shown on Christmas Day on BBC One.