Casey was seen becoming distressed in the clip as she paced around the rehearsal room and was fanned down by her co-stars.
“I’m having an anxiety attack,” Casey then said.
Speaking about her panic attack, Casey confessed the performance is the most she’s ever been out of her comfort zone.
“Being the only plus, plus size woman in this cast, it’s confronting. I struggle with anxiety on a daily basis, I could feel it creeping in," she said.
"It was a massive thing for me to take on board," Donovan told The Morning Show.
"It's taken me many years to be confident within my own body and stand my ground and go, I'm fit, I'm healthy, and I can do amazing things with my life.
"To bare half of me, when usually I like the lights off and for nobody to really see me in that state, it was a big thing to stand there and go, I am me, I am confident - this is who I am."
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