Sienna has been interfering in Darren and Nancy's relationship since she started working at The Dog in the Pond.
Speaking to Digital Spy at the 2013 British Soap Awards, Passey hinted at Sienna's motivations, why the Osbornes have caught her eye and where things might be heading next.
Watch our red carpet chat with Passey by hitting play below:
The actress also pondered whether Sienna is a villain and discussed the dark side of her on-screen father Patrick (Jeremy Sheffield).
Hollyoaks fans have seen Nancy on a downward spiral this year as she has developed an addiction to painkillers.
Sienna has been aware of the problem for a few weeks, but fans have been left to wonder whether she will be a friend or foe for the popular character.
Hollyoaks airs weeknights at 6.30pm on Channel 4, with first look screenings at 7pm on E4.
Photo gallery - British Soap Award winners in pictures:
Digital Spy Soap Scoop video - press play below to watch Amie Parker-Williams reveal gossip on Tina's labour scenes in Coronation Street, a baby bombshell in Emmerdale, danger for Dodger in Hollyoaks and a possible romantic reunion in EastEnders.