The leaking of the video triggered an outpouring of sympathy for Griveaux in France, where politicians and the media have long dismissed sex scandals as private affairs.
Pavlensky and de Taddeo were taken into custody in Paris on Saturday and questioned for two days.
Her lawyer Noemie Saidi-Cottier confirmed that her client had received the messages from Griveaux but denied that she had kept it with a view to using them against him.
Woman charged over sex video that tripped up Macron ally
Pavlensky, who has a long record of radical protests, received asylum in France in after falling foul of Russian authorities.
Description: Pavlensky, who made global headlines in when he nailed his scrotum to Red Square in Moscow as a form of political protest, told AFP last week that he posted the video of a year-old who had made families a core theme of his campaign.