The Jordanian authorities are violating people's right to free speech and undermining the credibility of reform efforts, a human rights group has said.
The charges related to an article about King Abdullah's alleged intervention in a corruption investigation, it added.
HRW said the case was the fifth such incident in Arab kingdom this year.
Sahar al-Muhtasab and her brother Jamal al-Muhtasab, who both worked for Gerasa News, had been charged on 23 April, a statement said.
They had both worked on an article that quoted a member of parliament as saying King Abdullah had issued instructions to members of a parliamentary committee not to refer a former minister to court on corruption charges.
Ms Muhtasab told HRW that a military prosecutor at the State Security Court had insisted King Abdullah was at the forefront of the fight against corruption, and that it was forbidden to imply otherwise.
The prosecutor charged them both with "subverting the system of government in the kingdom", a crime that article 149 of Jordan's penal code punishes with hard labour.
Ms Muhtasab was released on 5,000 Jordanian dinars' ($7,050; £4,366) bail, but the prosecutor ordered her brother detained without bail for 14 days at a prison in the city of Salt, west of Amman, where he remains.
Christoph Wilcke, HRW's senior Middle East researcher, said: "Jordan cannot claim to be making democratic reforms while prosecutors hunt down journalists doing their job."
The incident is the latest in a series in which people have faced charges for making speeches or attending demonstrations deemed critical of the government.
In January, a man was charged with "undermining his majesty's dignity" for burning a poster of King Abdullah. A former MP was charged the following month with "advocating a republican form of government". And in March, two separate groups of protesters were arrested in Amman.
"Jordan's talk of reform is meaningless as long as the law deprives citizens of meeting and speaking freely, especially about politics and their leaders," Mr Wilcke said. "The kingdom risks earning a reputation for repression and intolerance."