Interesting theory except that, from the in game tone and the cards themselves the Exo stranger has already seen the outcome of the battle with the darkness countless times before. She's not looking for her wife or anything like that but, is instead looking for a timeline where the light wins so that she can presumably take the knowledge of how to win back to her own reality. She skips realities within the time stream but, always goes to the point in time (within those realities) where she has managed to ascertain a turning point in the war against the darkness occurs. One such point is when you "Go down into the pit" upon finding the dead guardian at the gates to Crota's temple. She likely plays a more important role in the story in Destiny 2 given that you have clearly gotten so much further than any of her previous observations. She is basically curious as to what is so different about you. In the other timelines, due to variations in such things as who the ghost revived, how you discovered the temple, your fuzzy logic in dealing with the same situations in a slightly different but, significant way. All of these things have meant that you have succeeded and become more powerful where the others she observed got cut down, went into the pit and didn't return etc. etc. As for her identity. That depends on who occupied which role in her reality. She could easily be Maya, she could have not chosen to marry in her reality etc. etc.