Task: Question Answering
Input (English): Passage: After leaving the army in January 1919, Grainger refused an offer to become conductor of the Saint Louis Symphony Orchestra and  resumed his career as a concert pianist.  He  was soon performing around 120 concerts a year, generally to great critical acclaim, and in  April 1921 reached a wider audience by performing in a cinema, New York's Capitol Theatre. Grainger  commented that the huge audiences at these cinema concerts often showed greater appreciation for his playing than those at established concert venues such as Carnegie Hall and the Aeolian. In the summer of 1919 he led a course in piano technique at Chicago Musical College, the first of many such educational duties he would undertake in later years.Amid his concert and teaching duties, Grainger found time to re-score many of his works (a habit he continued throughout his life) and also to compose new pieces: his Children's March: Over the Hills and Far Away, and the orchestral version of The Power of Rome and the Christian Heart both originated in this period.   He also began to develop the technique of elastic scoring, a form of flexible orchestration  which enabled works to be  performed by different numbers of players and instrument types, from small chamber groups  up to full orchestral strength.In April 1921 Grainger moved with his mother to a large house in White Plains, New York. This was  his  home for the remainder of his life. From the beginning of 1922 Rose's health deteriorated sharply; she was suffering from  delusions and nightmares, and became  fearful that her illness would harm her son's career. Because of the closeness of the bond between the two, there had long been  rumours that  their relationship was incestuous;  in April 1922 Rose was directly challenged over this issue by her friend Lotta Hough. From her last letter to Grainger, dated 29 April, it seems that this confrontation unbalanced Rose; on 30 April, while Grainger was touring on the West Coast, she jumped to her death from an office window  on the 18th floor of the Aeolian Building in New York City. The letter, which began "I am out of my mind and cannot think properly", asked Grainger if he had ever spoken to Lotta of "improper love". She signed the letter: "Your poor insane mother". 
Question: Who became fearful that her illness would harm her son's career?
Output (English): Rose.