Later in the year, she reached her second semifinal at the Japan Women's Open, again coming through qualifying, while also scoring her first victory over a top-20 player, the top seed Kristina Mladenovic.

At the 2018 Australian Open, she appeared in the Grand Slam main draw for the first time as a direct entry[4] and recorded her first major win over Misa Eguchi.

[7] On her debut at the French Open, she entered the main draw as a lucky loser and recorded a first round win over Jéssica Bouzas Maneiro,[8] then losing her next match to Marie Bouzková.

[9] At the Jasmin Open, Fett reached the second round defeating Mayar Sherif[10] before losing to Sara Sorribes Tormo in three sets.

[11] The following week at the 2024 Thailand Open 2, she reached the quarterfinals after defeating Zheng Saisai[12] and eighth seed Varvara Gracheva by retirement,[13] before going out to eventual champion Rebecca Šramková.