The accused, who has not been named, faces several years in jail if found guilty of belonging to the movement of US-based cleric Fethullah Gulen, which has been branded a terror organisation by Ankara, the reports said.
At the trial in the southern city of Karaman, prosecutors accused her not only of membership of the group, which Turkey calls FETO, but said she led one of its local women's organisations.
Gulen, an Islamic preacher who lives in exile in the US state of Pennsylvania, denies any link to the botched putsch in July 2016.
The prosecutors said they have electronic proof of the woman's alleged actions against the Turkish state that were uncovered during raids at her apartment in Turkey.
The Turkish-born woman, who became a German national about 15 years ago, was arrested in August 2016, becoming the first German citizen to be detained after the attempted overthrow of President Recep Tayyip Erdogan.
She was granted conditional release in September but not allowed to leave Turkey.
But her case is far lower in profile than that of Deniz Yucel, a correspondent for the Die Welt daily newspaper, whose arrest in February on terror charges sparked outrage in Germany.
German journalist Mesale Tolu has been held on similar charges since May, while human rights activist Peter Steudtner was arrested in a July raid.
At least 10 Germans are currently detained in Turkey for political reasons, according to the German foreign ministry.
Relations between the two NATO allies have soured after Berlin sharply criticised Ankara over the crackdown that followed the coup attempt.
The escalating tensions have split the Turkish community in Europe's top economy, the largest diaspora, which is a legacy of Germany's “guest worker” programme of the 1960s and 70s.