The court in the northeastern town of Laon also ordered the woman to do 210 hours of community service that included repairing the damaged graves.
More than 70 metal crosses were broken or torn off the tombs at the Champ-de-Manoeuvre cemetery outside Laon at the weekend, with a Jewish Star of David on one of them also damaged.
The woman and a companion who is younger than 16 were arrested on Monday and admitted to vandalising the tombs while two of their friends drove motorbikes around the cemetery.
The minor also appeared before a judge Wednesday and was put under judicial supervision until a hearing in a children's court due in October.
The two bike riders have also been detained but have not yet appeared in court.
Police said Monday the youngsters had been drinking alcohol and held a motocross rally in the cemetery. They appeared not to have been motivated by xenophobia or anti-German feeling, police said.
The cemetery houses the remains of nearly 3,500 German soldiers killed in battles throughout World War I, between 1914 and 1918.