Nilsson gained her first international experience at the European Youth Olympic Festival (EYOF) 2015 in Tbilisi where she won the silver medal in the high jump with a jump of 1.80 metres. The following year, again in Tbilisi, she won the 2016 European Youth Athletics Championships high jump with a 1.82 metres jump. Nilsson gained more international experience at the 2018 U20 World Championships in Tampere, and at the 2019 European Athletics U23 Championships in Gävle.