The 'Modern Family' star wrote a series of angry Tweets about the 'Call Me Maybe' singer's scheduled appearance in the New York musical, saying she's ''hesitant'' about whether she will be able to pull the part off.
She wrote: ''Today's a meltdown day. Carly Rae Jepsen is going to be Cinderella??? On Broadway??? NOT OK WITH THIS.(sic)''
Looking to the show's current star, Laura Osnes, she then tweeted: ''Tell me it's gonna be OK @LauraOsnes.''
Sarah then added: ''Hoping she will be amazing. I'm hesitant though...''
Carly is set to take on the role for 12 weeks starting on February 4. It is not known if Sarah, 23, had been auditioning for the same part, but she sought to clarify she does not have anything personal against Carly.
She tweeted: ''To avoid anyone assuming things? My previous tweets do not mean that I'm not a Carly Rae Jepsen fan. The end.''
While Carly, 28, has not commented on Sarah's feelings about her casting, the Canadian singer says she's fulfilling one of her lifelong dreams by appearing on Broadway.
Speaking about the part, she said: ''Broadway has been a dream of mine since I was a little girl, and I look forward to working with this incredibly talented cast to tell this classic tale.''
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