She is remembered for performing in several modernist works, including those of Krzysztof Penderecki, Per Nørgård and Ib Nørholm.
[3] As a result, Guillaume spent her early childhood in France, Peru and Sweden, becoming fluent in several languages.
When she was 18, she entered the Royal Danish Academy of Music, studying under the tenor Thyge Thygesen.
[1] In 1974, she was engaged by the Royal Opera where she performed as lead mezzo-soprano in a wide variety of works, including Così fan tutte, Tancred, Der Rosenkavalier, The Devils of Loudun, Orpheus and Eurydice, Dido and Aeneas and Carmen.
[5] Among Guillaume's many awards include the Tagea Brandt Rejselegat (1977) and her distinction as a Knight of the Order of the Dannebrog (1985).