[3] The same year, her father was arrested and deported to Siberia for participating in the Sietynas organization which smuggled the banned Lithuanian publications from East Prussia.
In Moscow, she completed four semesters at the history and philology section of the Poltoratskaya's Higher Courses for Women [ru].
[2] In 1918, she returned to Lithuania and became a teacher of history, geography, and Russian language[2] at Marijampolė Realgymnasium established by attorney Andrius Bulota.
Her private students included future diplomat Stasys Lozoraitis Jr. and archaeologist Rimutė Jablonskytė-Rimantienė [lt].
Three of her sisters (including her brother-in-law Pranas Čepėnas) retreated to Germany ahead of the advancing Red Army and ended up in United States, Australia, and Canada.
[3] After the return of the Soviet regime in August 1944, Lastienė briefly taught at the University of Kaunas and organized courses for workers and farmers.
[2] Together with Tadas Petkevičius and three others, she authored a memorandum addressed to Western powers on the Soviet occupation and worked with Petras Klimas to have it translated to French and smuggled abroad.
[2] Lastienė corresponded with her brother-in-law historian Pranas Čepėnas and assisted him in collecting data for the 35-volume Lietuvių enciklopedija published in Boston.
[3] Lastienė also translated and published several fiction works: the play Inno del primo maggio by Pietro Gori (1920), the comedy The Wood Demon by Anton Chekhov (1921), the play Autumn Violin by Ilya Surguchov [ru] (1922), and the novel Nomads of the North by James Oliver Curwood (1937).