A member of the Prosvita cultural movement, she worked to establish a Ukrainian literary tradition through completing Ukrainian-language translations of Russian, French, and English literature under the pseudonym Olena Zirka.

Her efforts to document the life and work of her sister, the poet Lesya Ukrainka, culminated in an extensive chronology that was published posthumously in 1970.

Olha Kosach was born in 1877 in the city of Novohrad-Volynskyi (at the time situated in the Russian Empire; now Zviahel, Ukraine).

[6] After graduating from the medical institute in 1904, she married Mykhailo Kryvyniuk [uk], but her parents struggled to accept her rejection of a church marriage, which she viewed as demeaning to women, in favor of a civil partnership.

[1][2][4][5] Her work aimed to shape Ukraine's literary tradition and thus its national identity, particularly during the Ukrainian War of Independence.

[1][2] During World War II, Kosach-Kryvyniuk fled in 1944 to Prague, stopping in Lviv to deposit the family archive with the literary critic Maria Derkach [uk] for safekeeping.