Born in Hiden, Bertelsmeier received piano lessons from Barbara Szczepanska and composition lessons from David Graham as a schoolgirl. After graduating from high school, she studied piano with Pavel Gililov at the Hochschule für Musik und Tanz Köln (diploma 2005) and composition with Wolfgang Rihm at the Hochschule für Musik Karlsruhe (diploma 2008, concert exam 2011). She also completed a master's degree in musicology in 2009. Her works are performed at international festivals and by various performers, such as the Arditti Quartet, Quatuor Diotima, Ensemble Modern, Ensemble ascolta, Ensemble recherche, Fukio Saxophone Quartet, , Marc Bouchkov, Erik Nielsen, Christoph Eschenbach, Tabea Zimmermann, Orchester Nationale de Lorraine, , Bamberger Symphoniker and by members of the Berliner Philharmoniker. In 2017, her orchestral work for the 80th anniversary of the Bombing of Guernica was premiered for the Bilbao Orkestra Sinfonikoa with choir and children's choir.