[9] The Dutch international player enjoyed a very successful period with Die Wölfinnen, winning two Frauen-Bundesliga titles and a remarkable five consecutive DFB-Pokal Frauen Cups.

[10] She started both the 2020 and 2023 UEFA Women's Champions League finals for Wolfsburg, but narrowly missed out on European glory on each occasion as Lyon and Barcelona emerged victorious with 3-1 and 3-2 wins respectively.

On 2 July 2024, having announced back in May that she was set to leave Wolfsburg upon the expiry of her contract, Janssen signed for Manchester United on a three-year deal with the option to extend for a further year.

[13] Janssen moved into a defensive midfield role during her initial months in the team and scored her first United goal on 8 December in a 4-0 win over Liverpool, whilst also providing two assists.

[14] Janssen played for the first time for a Junior selection of Royal Dutch Football Association on 17 March 2010 at the friendly match of U-15 national team against England.

[19] Capturing the support of the entire nation, Sarina Wiegman's side beat Sweden and England in the quarter-finals and semi-finals respectively without conceding a goal in order to reach the final against Denmark.

The Dutch won the final 4-2 to secure their very first UEFA Women's Championship title and Janssen featured in the historic match when she replaced Desiree van Lunteren in the 57th minute as a substitute for the Oranje.

Janssen played in victories against Zambia (10-3), China (8-2) and the 3-3 draw with Brazil, where she scored the final goal to produce a 3-3 scoreline, befire losing on penalties to world champions USA in the quarter-finals.

On 31 May 2023, Janssen was named as part of the Netherlands provisional squad for the 2023 FIFA Women's World Cup and she featured for the team which reached the quarter-finals of the competition, before losing 2-1 after extra-time to eventual tournament winners Spain.