The court ordered Mesale Tolu on Wednesday to remain in jail pending trial over accusations of membership of the MLKP, a communist party with links to armed Kurdish groups.
Five other suspects were also remanded while eight people were released.
A total of 18 people face up to 20 years in jail over charges of being a member of a terrorist organization and publishing terrorist propaganda.
Tolu said during the Wednesday hearing in Silivri, near Istanbul, that she was innocent and demanded her immediate release.
“I have not committed any of the above mentioned crimes and have no connection with illegal organizations. I demand my release and my acquittal,” said Tolu, who was arrested in April and has been living with her three-year-old son in jail over the past five months as her husband has also been detained.
Tolu is among 11 German nationals caught in the wheels of a sweeping crackdown that unfolded following an unsuccessful coup last summer. The arrests have badly hit already strained ties between Germany and Turkey.
German Foreign Minister Sigmar Gabriel reacted to the Turkish court’s extension of Tolu’s arrest, urging Turkish officials to immediately release her.
“We demand a fair trial, based on the rule of law. Above all, what matters now is speed so that Mesale Tolu can be released as soon as possible,” Gabriel said in an interview on Wednesday.
Berlin maintains that Turkish officials have gone well beyond the rule of law by jailing some 50,000 people over links to the coup and other terrorism-related charges. More than 150,000 people have also been dismissed from their jobs across Turkey over similar allegations.