Smeets was working on her thesis in mathematics, on a subject within number theory, at Leiden University when she started the blog Wiskundemeisjes ('Math girls'), on 14 March 2006, together with Jeanine Daems.

She completed her PhD at Leiden in 2010; her dissertation, On Continued Fraction Algorithms, was supervised by Robert Tijdeman and Cornelis Kraaikamp.

On 19 October 2011, the book Ik was altijd heel slecht in wiskunde (I have always been bad at mathematics) appeared, which she wrote together with Jeanine Daems.

Begin 2012, Smeets co-presented eight editions of the KRO-program De Rekenkamer, replacing Sofie van den Enk.

Furthermore, she participated in the NCRV's television quiz De Slimste Mens in August 2014, almost reaching the final round.