Demireva did not reach the final at the 2006 World Junior Championships, but won the silver medal at the 2008 World Junior Championships.

[1] At the Olympic Games in Rio de Janeiro 2016 Demireva won a silver medal, jumping 1.97 m. She also won two consecutive silver medals at the European Championships (2016–18).

Demireva was the 2016 Bulgarian Sportsperson of the Year and came in second place during the 2018 edition of the award.

[5] Her personal best jump is 2.00 m (6 ft 6+1⁄2 in), achieved in June 2018 at the Diamond League meeting in Stockholm.

[1] This biographical article relating to Bulgarian athletics is a stub.