Smits started her youth career with OJC Rosmalen at the age of six.[2] She spent eight years there playing alongside boys before moving to Brabant United. In 2015, she moved to CTO Eindhoven.[3]
In May 2017, Smits signed her first professional contract with Eredivisie club Twente.[4] She made her debut on 1 September in a 3–0 league win against Zwolle. She scored in 58th minute of the game before being replaced by Bente Jansen.[5] She scored 25 goals in 21 league matches during the 2018–19 season to help her club win the league title.[6]
In February 2019, it was confirmed that Smits would join PSV prior to the 2019–20 season.[7] She was top Eredivisie scorer when football leagues across Netherlands were suspended by Dutch government in March 2020 due to the COVID-19 pandemic.[8]
On 15 September 2020, German Frauen-Bundesliga club VfL Wolfsburg announced that Smits has signed a three-year contract with the club, which would start in July 2021.[9] On 5 June 2021, she played her last match for PSV in the cup final against ADO Den Haag. She scored the only goal in the match to win PSV's first trophy in its history. With 52 goals from 45 matches across all competitions, Smits left the club as PSV's all-time top scorer.[10]
During her only season with Wolfsburg, Smits won the German league and domestic cup titles.[11] On 3 June 2022, her contract with the club was terminated by mutual agreement.[12] She returned to her former club PSV on the same day, signing a three-year contract until June 2025.[13]
With 15 goals from 16 matches, she holds the record for most caps and goals for the Netherlands under-16 team.[17] Similarly, with 33 goals from 38 matches, Smits is the most capped player and all-time top scorer of the Netherlands under-19 team.[18]
Smits made her senior team debut on 4 March 2020 in a friendly against Brazil. She came on as an 84th-minute substitute for Vivianne Miedema before the match ended in a goalless draw.[19] On 16 June 2021, Smits was named as a stand-by player for 2020 Olympics.[20] On 20 July, she was added to the final squad as a replacement for injured Sherida Spitse.[21]