At Rhodes University in Grahamstown, Eastern Cape, she read human kinetics and ergonomics, and ichthyology and fisheries studies for her undergraduate education.

[9] In November, Thornycroft qualified for the 2012 London Olympic Games by finishing first in the women's single sculls at the Africa Continental Qualification Regatta held in Alexandria, Egypt.

[2][7] In the buildup to the Olympic Games, Thornycroft went on to compete in the Paulo D'Alorja regatta held in Italy, she attained sixth place in Final A race.

[6] At the 2012 Summer Olympics in London, Great Britain, Thornycroft managed to attain fourteenth place overall as she finished second in the Final C race.

She had training camps in Italy and Germany before participation at the 2013 World Rowing Championships in Chungju, South Korea where she finished fourth in the Final B race.

At the 2014 World Rowing Championships held in Amsterdam, Netherlands, Thornycroft achieved a second-place finish in the Final D race and nineteenth overall.

[12][13] Micheen came first in the women's single sculls event at the 10th African Rowing Championships (which ran from 16–18 October) held at the Boukerdane Dam in Sidi Amar, Tipaza, a town in northern Algeria.

Micheen came first in the women's single sculls event at the 2015 African Continental Qualification Regatta in Tunis, Tunisia and as a result, qualified for the 2016 Olympics.

[18][19] In February, Thornycroft participated in the women's single sculls event at the Buffalo Regatta in East London, Eastern Cape, South Africa, where she finished first.