Hence the "was". The Stranger used to be a guardian. A Bladedancer. She is the sister of the Anna chick, the only non Titan to fight at the battle of the 6 Fronts. At one point she was human. However, she traded her human body for an exo body, so that she could travel in time using the FWC machine, to stop some catastrophic event. When she swapped bodies like this, she lost her Light. So her Exo body is "not born in the Light", but her human body was. Unfortunately, she failed in her attempt to stop the event from happening, but continued to try in different timelines. Of course, the exact event she is trying to avoid, she doesn't have time to explain why she doesn't have time to explain. #TitanMasterRace