Kaleyn debuted as a senior in the 2016 season, she finished 10th in the all-around at the Baltic Hoop International tournament. In her next event she finished 4th in the all-around at the Lisbon Senior International Tournament, she qualified for all the apparatus finals taking silver in hoop, ribbon, clubs and silver in ball. She then finished 10th in the all-around at the Corbeil-Essonnes Cup. In the 2017 season, Kaleyn competed at the Moscow senior International Tournament where she made a breakthrough winning silver in the all-around. She won bronze in the all-around at the 2017 Bulgarian National Championships behind Neviana Vladinova and Katrin Taseva who took the gold and silver medals respectively. She then competed at the 2017 Tashkent World Cup finishing 4th in the all-around behind teammate Katrin Taseva and qualified to 3 event finals taking bronze in clubs and placed 7th in hoop and ball. Her next competition was at the 2017 Baku World Cup where she finished 9th in the all-around behind Nicol Zelikman. On May 3–7, Kaleyn won gold in the all-around at the MT Sofia Cup. On May 12-1, Kaleyn competed at the 2017 World Challenge Cup in Portimao where she finished 4th in the all-around behind Victoria Veinberg Filanovsky, she qualified to 3 event finals taking bronze in clubs, finished 5th in hoop and 6th in ball. Kaleyn competed at the quadrennial held 2017 World Games in Wrocław, Poland from July 20–30, however she did not advance to any of the apparatus finals. In the 2018 season, Kaleyn participated at the 2018 Grand Prix Moscow, finishing 10th in the all-around. She qualified to 3 finals, winning gold with ball, silver with hoop and bronze with ribbon. On March 30-April 1, Kaleyn began the World Cup events competing at the 2018 Sofia World Cup finishing 6th in the all-around, she qualified in 2 apparatus finals, taking bronze in hoop and finishing 5th in ball. On March 23–25, Kaleyn competed at the 2018 Grand Prix Thiais, where she won the bronze medal in the all-around competition ahead of teammate Katrin Taseva. In the apparatus finals she won bronze with ball, clubs, finished 5th in hoop and 9th in ribbon. On April 20–22, at the 2018 Tashkent World Cup, Kaleyn finished 9th in the all-around and qualified to 2 apparatus finals: she won bronze in hoop and finished 8th in ribbon. On April 27–29, Kaleyn competed in a WorldChallenge Cup event at the 2018 Baku World Cup where she finished 9th in the all-around, she qualified in 2 apparatus finals taking silver in clubs and finished 4th in hoop. At the 2018 World Championships, held in her hometown of Sofia, Kaleyn won a silver medal with the Bulgarian team. Kaleyn started her 2019 season competing at the GCP Lisbon senior International Tournament where she ranked 5th in the all-around. She qualified to 2 finals, winning gold with hoop and bronze with ball. On March 28-April 1, she competed at the 2019 Grand Prix Thiais, where she placed 4th in the all-around behind Arina Averina, Linoy Ashram, and Dina Averina. She qualified for 3 apparatus finals, winning silver with ribbon and placing 5th with ball and 8th with hoop. Kaleyn then competed at the 2019 Pesaro World Cup, winning her first World Cup all-around medal by finishing in 3rd place behind Dina and Arina Averina. She qualified for 3 apparatus finals, winning silver in ball, placing 4th in hoop, and 5th in clubs. At the 2019 Tashkent World Cup, Kaleyn won silver in the all-around and qualified to all 4 apparatus finals; she won silver with ball and ribbon and finished 7th with clubs and 8th with hoop. On April 16–19, she competed in the 2019 European Championships with her teammates Katrin Taseva and Neviana Vladinova, with whom she won the bronze medal in the team event. She qualified for 3 apparatus finals, winning bronze in ball and ribbon and placing 7th with hoop.
