She is tall, tan and has dark keen eyes.
Rios was working in the military as a Corporal with a team including Jackson, Mendez and Fallon when a grenade explodes in the building that they were raiding. After the building fell on top of her, her last thoughts were of needing to get free. She then falls through the floor into the basement and realises that she can pass through walls. Rios reports her ability to her Sergeant and Stell decides that instead of capturing her, to recruit her into EON.
Agent Rios works at EON as Stell's second-in-command and is one of the few staff that view EOs as people. When Dominic is hacking the system to prevent Eli's release, she walks into the locked room and arrests him. Later when interrogating him, Dom goes into the shadow realm and uses staples from her files to pick his handcuffs and then locks them on her. Additionally when Victor is escaping after Dom is dead, she surprises him and matches his attacks, Victor finally wins when he forces her to electrocute herself. It's likely that she is still alive as she only "collapsed, unconscious."
Rios is able to move through walls and floors at will.