Emily will play the role of Holly Golightly (the iconic character made famous by Audrey Hepburn) in the musical adaptation of the movie classic and told fans she is "so excited" to be making her stage debut later this year.
Taking to Instagram, Emily revealed her new role. She said: "I'm SO excited to share the news that I'll be making my stage debut as Holly Golightly in Breakfast at Tiffany's in the spring! Hope to see you all there!"
She will share the part with Pixie Lott who announced she would be joining the cast back in June last year. Pixie will kick off the Breakfast At Tiffany's UK tour this month, before Emily takes over between 2 May and 11 June.
Pixie will then take up the role of Holly once again to finish the remaining tour dates across the country, before heading to London's West End.
News of Emily's addition to the cast comes after former Emmerdale star Verity was forced to pull out.
Yesterday, Verity announced she is pregnant and expecting her first child with husband Dominic Shaw. She took to Twitter to share her baby joy and a photo of herself and Dominic looking over the moon at their news.
Verity told fans: "Yey! @dominicmshaw and I are expecting our first baby this summer! So excited!!"
Her pregnancy has meant Verity can no longer take part in the Breakfast At Tiffany's tour, but the 30-year-old still urged people to go and see the show.
She tweeted: "I can't thank @NikolaiFoster and the entire @tiffanysonstage team enough for their support. They have been wonderful! To those that may be disappointed my sincere apologies. I understand theatre's will offer refunds to those who wish. The show WILL be fab!"
Verity's baby news comes three years after she and Dominic tied the knot. They married in March 2013.
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