Original: Doctors worried that, due to her cerebral palsy, Lucy would never be able to speak or use sign language to communicate with her deaf sister, but after production of the first volume, Lucy began to sign, and later, to speak.
Simplified: Doctors worried that, because of her cerebral palsy, Lucy would never be able to speak or use sign language to communicate with her deaf sister, but after the first volume was made, Lucy started to sign, and later, to speak.