IMO the real Osgood died at the hands of Missy. The Osgood strutting about during Invasion/Inversion was the Zygon duplicate. Now we have Bonnie also taking the form of Osgood. The Zygon-Human peace is being maintained by two Zygons, who would rather be Osgood than themselves.
Except... would the real Osgood, one familiar with the Master's record, have been suckered in by Missy the way she was? The Osgood of these last two episodes certainly wouldn't be. (Don't even get me started about Missy's 'guards'...)
The Osgood we saw in Inversion of the Zygons seemed not to know some basic facts about the Doctor as well. Like what TARDIS stood for, and others things that I can't recall atm. However, it did seem odd to me when I first watched the episode that Osgood would be asking these types of questions.
I'll have to watch it again to get specifics.
That's easy, the Osgood the Doctor was talking to at the end with the question mark shirt on was Bonnie, the Osgood who then turned up wearing a duffel coat was the real Osgood, although obviously she may not be the real Osgood
