So her mom brought her to a doctor to find out what was wrong, and he made a startling diagnosis.
"Mrs. Lynne, Gillian isn't sick," he said. "She's a dancer. Take her to a dance school."
She did. As education scholar Ken Robinson says in his TED Talk on creativity, Gillian went onto the Royal Ballet and into musical theater history.
"Lynne's been responsible for some of the most successful musical theater productions in history; she's given pleasure to millions; and she's a multimillionaire," Robinson says. "Somebody else might have put her on medication and told her to calm down."