Pellegrini started in Formazza in December 2007 for the first time in the cross-country Alpine Cup and came in 21st place over 5 km classic and tenth place in the 10 km mass start race. At the U23 World Championships in 2009 , she came 30th in the skiathlon . In 2011 she achieved her first podium positions in the Alpine Cup with second place in Ramsau am Dachstein and third place in Pokljuka over 5 km freestyle. At the beginning of the 2013/14 season, she made her debut in Davos in the cross-country skiing world cup and finished 50th in the 15 km freestyle. In the further course of the season she finished in the top ten 11 times in the Alpencup. She won her first Alpine Cup victory in the pursuit race on the mini tour in Campra and won the mini tour with it. In addition, she achieved second place in the 10 km freestyle in Campra and second place in the 15 km mass start race in Rogla and came second in the overall ranking of the Alpine Cup at the end of the season. In 2015 she won the Marcialonga Lights over 33 km. In the 2016/17 season she won her third victory in the Alpine Cup in Planica over 10 km freestyle. At the Nordic World Ski Championships 2017 in Lahti , she came 28th in the 30 km mass start race. In the 2017/18 season she came with six podium finishes, including four victories, and came second in the overall ranking of the Alpine Cup. At the season highlight of the 2018 Winter Olympics in Pyeongchang , she ran to 38th place over 10 km freestyle and 35th place in both skiathlon and 30 km mass start races.
In the 2018/19 season, Pellegrini finished 27th in the Tour de Ski 2018/19 and thus scored her first World Cup points. In addition, she achieved sixth place in the overall ranking of the Alpine Cup with seven top ten placements, including second place over 10 km classic in Planica . At the Nordic World Ski Championships in 2019 in Seefeld in Tyrol , she finished 35th in both the skiathlon and the 30 km mass start race. In the following season she was third with four and one second place, second in the overall ranking of the Alpine Cup.