A Caddo Nation Tribal leader from Oklahoma was released Saturday after spending two days in a North Dakota jail.
Her family said they are outraged and that she was an innocent bystander at the protests against the Dakota Access Pipeline.
Tamara Francis-Fourkiller was visiting the Standing Rock Sioux tribe to advise them on negotiations with the pipeline.
She was arrested while trying to visit the protest camps near the town of Cannon Ball.
An anonymous donor paid $2.5 million late yesterday to release everyone who has been arrested at the pipeline in recent months.
More than 140 people were arrested Thursday when the protests escalated into violence.
This weekend, leaders on both sides tried to ease the tensions.
Sioux Chief Arvol Looking Horse shook hands with police officers in a public show of cooperation.
The chief said he wants the protest to be more peaceful but that his tribe isn't giving up.
"They're not going to back down, we're not going to back down either," Looking Horse said.
A rally is planned for Monday at 3 p.m. at the capitol building in Oklahoma City to show support for the Standing Rock Sioux tribe.
Organizers said they want to show they are frustrated with the way protesters in North Dakota have been treated.
They are encouraging people to bring drums and perform street theater.