The 17-year-old is now assured of at least a silver medal from the completion and will stake a claim for her second world title.
Zareen, who won the flyweight division gold medal at the inaugural edition of the AIBA Women's junior World Championship, has moved into the youth category and fights in the bantamweight division.
She registered a comprehensive victory over Desire Galli from Italy in the quarters to advance to the round of four. In the semi-finals, the Andhra boxer was up against another junior world champion Viktoriya Virt of Ukraine.
But on the day of the semi-finals in the Albena, the Ukrainian boxer was no match to the nimble-footed Indian. Zareen took the fight to Virt from the very beginning of the bout, never allowing her space to play her natural game.
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Some brilliant infighting with a volley of jabs helped her gain the advantage. She dominated the entire bout and made her place in the final with a victory on a unanimous decision.
"I adopted an aggressive approach from the very beginning and was hoping for a little more resistance from my opponent. But she became more defensive and took advantage of that. I hope to carry the same form in the finals as well," said the Indian teen, who will now fight for title against Yunzi Yuan of China.
Whereas in the junior group, upcoming boxer from Madhya Pradesh, Asha Roka (48kg) was beaten by Assyl Askarova of Kazakhstan. Both boxers will have to be content with a bronze medal performance from the championships.