Ms Khawaja was charged with being involved in an illegal gathering.
She told the BBC protesters would "keep trying to reclaim Pearl Roundabout".
"We are not going to give up," she added. "Whose determination is stronger – the people’s or the dictatorship? Only time will tell."
Ms Khawaja said she had not been mistreated while in detention.
"The only reason for that is because the government is afraid of bad media not because they respect my rights," she said.
Most of the demonstrators in Manama are from the Gulf kingdom’s Shia Muslim majority, which has long complained of discrimination at the hands of the Sunni royal family, the Al Khalifa, and wants democratic reforms.
On the uprising’s anniversary last Tuesday, police were deployed throughout the capital to prevent people reaching Pearl Roundabout.
There were, however, clashes in outlying villages. Police fired rubber bullets and tear gas at youths, who threw petrol bombs and stones.
On Monday, about 100 people tried unsuccessfully to reach Pearl Roundabout from the village of Sitra, south of Manama, activists said.
The march took place after a funeral for a protester who accidentally set himself alight while pouring petrol onto burning tyres, they added.
In a separate incident at another funeral in Sitra – this time reportedly for an elderly man who died after his house was hit by tear gas – a young man was left in a critical condition after being hit by a tear-gas canister.
At least 35 people were killed between February and March 2011, 30 of them civilians and five security forces personnel. Security forces were found by an independent human rights commission to have used excessive force and tortured detainees, including five who died.
Last week, Amnesty International said at least another 20 people had been killed since March "in the context of ongoing protests and excessive use of force by the security forces". Others put the death toll at 30.
