Just a assumption but there are references whil running the queens missions about Intel from the Brother's Crows. Now unless he is dr. Doolittle and can actually talk to Crows then I'm guessing he has a Intel group keeping tabs on events in the wild. The Stranger who seems to be shadowing your character and leads you to the Vex makes reference to "choosing a side" and "not being born of the light" which leads me to think that she is working for someone outside of the Tower. The Queens Brother possibly? Also during that convo at the Academy she is interrupted and says "have they spotted you" which again leads me to believe that she is with a group. Again making me think that she may be a member of the Crows. All just guess work though.