She founded and managed the girls' school Klosterskolan in Uppsala from 1855 to 1863 and was the principal of the Högre lärarinneseminariet (Advanced Seminary for Female Teachers) in Stockholm from 1863 to 1868.

In 1854, she married the teacher and librarian Pehr Adrian Thengberg (d. 1859) in Uppsala, where she was introduced in intellectual circles frequented by, among others, Per Daniel Amadeus Atterbom, Thekla Knös, Gunnar Wennerberg, and Malla Silfverstolpe.

In 1863 Miller Thengberg succeeded Hilda Elfving in the position of principal at the newly established Högre lärarinneseminariet in Stockholm.

Her rules became the target of public debate, which is said to have been caused by male teachers whom she had fired, with the support of Fredrika Bremer.

Miller Thengberg died in 1902 in Uppsala, Sweden, and is buried in Norra begravningsplatsen.