Lema, a former deputy of the main opposition Democracy and Development Party (CHADEMA), left her country in 2020 after receiving threats.
Lema returned to her country after the government changed its approach towards the dissidents.
Welcomed by the Kabbalah group in the city of Arusha, Lema served as a member of parliament in 2010-2020.
Tundu Lissu, the former presidential candidate of CHADEMA, also returned from Belgium in January.
Tanzanian President Samia Suluhu Hassan promised opposition leaders that their safety would be ensured.
Hassan’s successor, former President John Magufuli, faced criticism for his oppressive attitude towards dissidents before he passed away.