Sarah is a traveler found at the Canyon of Titan. When encountered, she is about to be robbed by Klink - and maimed by the explosion that kills Brother Marvin as he performs his duty. She will ask the Rangers to put her out of her misery and deliver her locket to David Barnes.
However, it's possible to kill Klink and protect Sarah from death, but it requires shooting him with a sniper at maximum range. She will immediately despawn along with Brother Marvin.