The Downton Abbey actress shone in Dolce & Gabbana co-ords while attending a Cinema Society screening of the movie in New York on Sunday (8 March).
She teamed her striking red and black outfit with Stuart Weitzman heels, elegant make-up and a classic updo for a modern day princess look.
Lily was joined at the screening by co-star Richard Madden, who plays Prince Charming to her Cinderella in the sure-to-be blockbuster film.
The movie, directed by Sir Kenneth Branagh, has already wowed Reveal's reviewer who was lucky enough to get a sneak peek!
For the rest of us, we have to wait until the end of the month to see Cinderella on our screens!
Richard – who played Robb Stark in Game of Thrones - told The Hollywood Reporter that Lily's Cinderella is no wimpy princess.
"This young woman in distress doesn't need a man to save her," he said. "That's totally irrelevant — she'd be fine without the prince, she'd get on with it."
As well as attending the screening last night, the on-screen pair took part in a Q&A at the Apple Store in Soho, New York.
Cinderella, directed by Sir Kenneth Brannagh, arrives in cinemas on 27 March.
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