She could be the last survivor of Venus. Knowing what the darkness can do she might be helping you so nothing bad can come to her as well. She is an Exo meaning she could live longer than other life forms. She also has a gun with technology never even thought to be possible, there is basically nothing salvageable on Venus, could this mean that she has went back in time, teleported, or possibly someone is supplying her with stuff. Who supplies never before seen materials? Agents of The nine. Maybe she has close ties with Xur or maybe another agent.