Harrison worked as a nurse and a public health administrator until Akana's death in 1943, when she took over his position as manager of a funeral home company.

In 1944, she publicly explored the idea of campaigning to succeed her husband in the Hawaii Territorial Senate, eventually announcing her candidacy in August of that year.

[1] All three siblings were boarding students at St. Andrew's Priory School from first through twelfth grades, and spent the summers at the Anglican church cottage in Kāhala.

[3] After graduating from St. Luke's in January 1926, she enrolled in a public health nursing program at the University of California, which ended in December of the same year.

[3] After her first husband, Senator Akana, died of a heart attack on April 16, 1943,[4] Harrison took his position as manager of Nuuanu Funeral Parlors.

[11] In January 1944,The Honolulu Advertiser reported that she was "being urged" to run for Territorial Senate as a Republican, having previously assisted her husband with the political campaign that led to his election.

[12] The same month, she told the Honolulu Star-Bulletin that she "[had] not said no, and [had] not said yes" to pursuing her husband's Senate seat, and that she would decide based on whether she would still be able to run her business and support her children.

[13] At the end of May 1944, the Hawaii Tribune-Herald reported that "[it seemed] an open question as to whether Mrs. Thelma Akana [would] seek election to the seat formerly held by her husband".

[14] In June, she visited the United States Capitol to discuss health conditions in the Territory of Hawaii, and subsequently attended the Republican National Convention as an alternate delegate.