They were later jailed for one year. Her husband, prominent artist Htein Lin, will also be released, the official said.
Sean Turnell was working as an adviser to Myanmar's civilian leader Suu Kyi when he was detained shortly after the coup in February last year.
In September, he and Suu Kyi were convicted by a closed junta court of breaching the official secrets act and jailed for three years each.
Kubota, 26, was detained in July near an anti-government rally in Yangon along with two Myanmar citizens and jailed for 10 years.
Families gathered outside Insein prison in Yangon ahead of the expected announcement, an AFP reporter said.