Osgood Survival Theories

"Spoilers!" -River Song

So if you've been surfing the interwebs then you've probably heard that Osgood is returning to Doctor Who. I have a couple theories on how she survived Missy killing her in "Death in Heaven." 

1. She's a Time Lord. Enough said. She could have used the ashes as the biological receptacle (excuse spelling) like the 10th Doctor did with his hand.
2. She's a Zygon. In "The Day of the Doctor", 10 and 11 make the zygons and humans forget if they're human or zygon. She could have killed the Zygon one and the human one is still alive.
3. Missy miniaturized her. It's possible that Missy never killed people. That remote thing of her's could actually just be a miniaturizing ray.
4. The new one is a past version. The Doctor might be meeting the past Osgood not the current one.

Tell me if you agree in the comments below. And as always, "Be your mythical best!"

-E