With the reveal of the Witch Queen having an ascendent realm we cannot kill her here. So lets say she has studied a ghost long enough and has utilized captured light in effect to revive herself afterwards leaving a dead osiris in her wake (if we kill her). How would you picture that encounter happening? Better yet... how would you play a role in her escaping? I personally feel like she would use her song to calm me into targetting petra and other guardians while she cowers behind me. Under her influence, I fight to reclaim control while she uses what is left of her magic to open a portal and leave. Mara, osiris, petra, and crow all watch on as the true betrayal never came from any of them... but was our guardian instead via Savathun's Song.