Question: Roy Galbriath Henderson taught what English contralto singer that died of cancer during the height of her career? 

Context articles: Francesca Vanini-Boschi
Sara Flower
Margaret Kennedy (singer)
Roy Henderson (baritone)
Kathleen Ferrier
Ann Henderson
Constance Shacklock
Norma Procter
Anne Collins (contralto)
Clara Butt

Francesca Vanini-Boschi (died 1744) was an Italian contralto singer of the 18th century.
 She is best remembered for her association with the composer George Frideric Handel, for whom she sang both in Italy and in London.
Sara Elizabeth Flower (c. 18201865) was a British-born contralto singer who became Australia's first opera star.
 She began a musical career in London in the 1840s but decamped to Australia late in 1849, when her professional future seemed secure.
 Soon after her arrival in Melbourne early in 1850 she began a career as the Australian vocal phenomenon of the era.
 In 1852 she appeares in Sydney in the first production in Australia of Bellini's opera "Norma".
 Flower was Australia's first diva.
Margaret Kennedy (died 23 January 1793) was a contralto singer and actress.
 She was best known for her performances in male roles, especially in the operas of Thomas Arne.
Roy Galbraith Henderson CBE (4 July 189916 March 2000) was a leading English baritone in the 1920s, 1930s and 1940s.
 He later became a teacher of singing, his most notable student being Kathleen Ferrier.
Kathleen Mary Ferrier, CBE (22 April 19128 October 1953) was an English contralto singer who achieved an international reputation as a stage, concert and recording artist, with a repertoire extending from folksong and popular ballads to the classical works of Bach, Brahms, Mahler and Elgar.
 Her death from cancer, at the height of her fame, was a shock to the musical world and particularly to the general public, which was kept in ignorance of the nature of her illness until after her death.
Ann Henderson {'1': ", '2': ", '3': 'RSA', '4': "} (11 October 1921– 13 March 1976) was a Scottish sculptor born in Thurso, Caithness, Scotland.
 Henderson taught sculpture at the Edinburgh College of Art for almost twenty years and was elected a member of the Royal Scottish Academy in 1973.
Constance Shacklock OBE (1913–1999) was an English contralto.
 After more than a decade of roles with the Covent Garden Opera Company, with other companies and on the concert stage, Shacklock performed for six years in "The Sound of Music" in London as the Mother Abbess.
 She taught singing at the Royal Academy of Music from 1968 to 1978.
Norma Procter (15 February 1928, Cleethorpes, Lincolnshire – 2 May 2017, Grimsby) was an English contralto who studied with Roy Henderson.
Anne Collins (29 August 1943 – 15 July 2009) was an English contralto known as versatile operatic singer, praised for her "beautifully warm and wide-ranging timbre, and impeccable diction".
 In a career that spanned nearly 40 years, she sang a wide range of operatic character roles and other classical pieces, including standard opera repertory, premieres, 20th century pieces, art song and other music.
Dame Clara Ellen Butt, DBE (1 February 1872 – 23 January 1936) was an English contralto.
 Her main career was as a recitalist and concert singer.
 Her voice, both powerful and deep, impressed contemporary composers such as Saint-Saëns and Elgar; the latter composed a song-cycle with her in mind as soloist.