Martha O'Donovan, 25, was granted bail
at a court hearing Thursday after being detained November 3.
"She has been released to US Embassy officials. That's all we can say," said Kumbirai Mafunda, a spokesman for Zimbabwe Lawyers for Human Rights.
O'Donovan was detained after reportedly tweeting that Mugabe -- one of Africa's longest-serving leaders -- is "a selfish and sick man." She denies wrongdoing.
The next hearing in her case is scheduled for Wednesday.
Her bail conditions include reporting twice a week to the police, surrendering her passport, not interfering with witnesses and residing at her home until the case is finalized.
Defense attorney Obey Shava of Zimbabwe Lawyers for Human Rights said Thursday that the charges against his client were "concocted."
"There is no substance in what the state is saying," he said. "It is not Martha O'Donovan which is the real target here. But the whole idea behind the charges is to discourage people from putting their ideas on social media, and it is about a clampdown on social media by the state."
O'Donovan, who works for a satirical video website, is the first person to be accused of plotting to overthrow the government since last month's creation of a cybersecurity ministry intended to police social media.
When the Ministry for Cyber Security, Threat Detection and Mitigation was announced, presidential spokesman George Charamba told reporters that the new office was intended to "trap all rats" that abused social media.
Mugabe has long been criticized for corruption and abuse of power. At 93, he has ruled Zimbabwe since 1980 with little opposition.