Wahl was born in Brussels, and earned a license in mathematics in 1998 at the Université libre de Bruxelles, advised by Jean-Paul Doignon.
Her undergraduate thesis concerned infinite antimatroids, and she published the same material in 2001 as her first journal paper.
[1] She completed a Ph.D. at the University of Oxford in 2001, with a dissertation Ribbon Graphs and Related Operads in algebraic topology supervised by Ulrike Tillmann.
[1][3] In 2008, Wahl won the Young Elite Researcher Award (Ung Eliteforskerprisen) of the Independent Research Fund Denmark (Danmarks Frie Forskningsfond).
[1][4] In 2016, she was elected to the Danish Academy of Natural Sciences.