On 12 May 2021, Nouwen agreed pre-contract terms on a three-year deal with Chelsea which commits her to the club until the summer of 2024.

On 10 October 2021, Nouwen made her first league start for Chelsea in a 2–0 victory against Leicester City, a game in which she would play 90 minutes.

[7] On 8 May 2022, Nouwen won her first league title as Chelsea lifted the FA WSL trophy on the final day with a 4–2 victory against Manchester United.

[8] On 1 December 2023, Nouwen sustained an anterior cruciate ligament rupture in a friendly with the Netherlands under-23 team against Scotland under-23.

On 4 March 2019, Nouwen made her debut for the Netherlands senior national team when she started and played 63 minutes in the 1–0 defeat for Poland.

[15] Two days later, on 6 March, she recorded her second international cap when she replaced Siri Worm in the 66th minute of the match against China PR.

[16] On 23 October 2020, Nouwen scored her first goal for the Netherlands senior national team in a 7–0 victory over Estonia which saw the side qualify for the Women's Euros in 2022.