McMillen graduated from Hacettepe University State Conservatory Department of Ballet in 1960 and joined Ankara State Ballet as a student and dancer of Dame Ninette De Valois at Ankara State Opera and Ballet the same year. She has worked at this institution as a dancer, instructor and choreographer from 1960 to 1977. From 1970 to 1974, McMillen received a scholarship from London Contemporary Dance School, where she studied Martha Graham Technique from Jane Dudley and Robert Cohen for four years. In 1972, she participated in the young choreographer’s competition held in Cologne with her first choreography. In 1973, McMillen went to The United States, where she received a scholarship from choreographer Merce Cunningham to study the Cunnigham Technique in New York and participated as a dancer in one of the choreographer's works. After returning to Turkey in 1974, she continued to work as a choreographer, instructor and manager at Ankara State Opera and Ballet and İstanbul State Opera until her retirement in 2006.
Pioneering modern dance ensembles in our country with academic and modern dance education, she exhibited her first modern dance choreography in Turkey with the Contemporary Dance Ensemble, which she founded between 1974 and 1975 with the support of Ankara State Opera and Ballet. From 1977 to 2006, McMillan worked as a choreographer, instructor and director at the İstanbul State Opera and Ballet, where she served as Chief choreographer from 1990 to 1993. Between 1979 and 2002, she participated in many national art organizations and was invited to stage her works at Ankara, İzmir and Mersin State Opera and Ballets. McMillen has been the Dance Director of the Europalya and Habitat Organization, held the Dance Festival with the support of Habitat Organization, and performed the duties of Dance Consultant and Member of the Board of Directors at the İstanbul Music Festival and Dance Consultant at the Ministry of Culture. Between 2002-05, McMillan founded the Cemal Reşit Rey Dance Theatre Ensemble of which she has served as the artistic director. She was awarded the Bimeras Award by the Consulate General of Belgium in İstanbul and the Bimeras Cultural Foundation for her contribution to the development of the art of dance in Turkey. McMillen, who was a member of the jury of the 2016 International Classical Ballet Competition, has successfully exhibited her various projects and works on national and international platforms between 1974 and 2012. She has participated in festivals and dance platforms held in Turkey, Great Britain, Germany, Austria, The Netherlands, Italy, United States, France and China as a dancer, choreographer and instructor. She has been invited to the Venice Dance Biennial for four consecutive years. McMillen, whose most recent work focuses on dance and video installations, continues her research and work for the development of the art of dance in Turkey by transforming the shows of the İstanbul Dance Theatre (İDT+) Ensemble, which she founded in 2005, into an interdisciplinary art event.