After joining the Walala Central College in 2014, it was her athletic instructor Susantha Fernando who influenced her to specialise in the 400m and 800m events.

[6] She tasted her first international experience during the 2016 Asian Junior Athletics Championships which was held in Ho Chi Minh City, where she was placed 6th in the women's 800 meter finals.

[9][10] She also claimed gold medals in 400m, 800m and 400m relay events at the 2018 South Asian Junior Athletic Championships which was held in Colombo.

[11] In April 2019, Kumarasinghe was part of the Sri Lankan 4 x 400 meter relay, which finished fourth at the 2019 Asian Athletics Championships at the Khalifa Stadium in Doha.

[12][13] She made her maiden South Asian Games appearance representing Sri Lanka at the 2019 South Asian Games and became the most successful athlete for Sri Lanka during the competition, claiming three gold medals in athletic events (400m, 800m and 4×400m relay).