I just responded to an anon and I don’t think that is the case. It would make more sense if they did those hallucinations and memories in Heaven Sent. The Doctor is trapped for years in that castle place, it makes sense that he would have hallucinations, memories and images sent to him in that episode. These images are from Hell Bent. What we know of Hell Bent is that it starts with the Doctor (like a western) walking to a diner. So I am of the theory that we are seeing Clara. I was not 100% convinced she died, but we shall know soon enough. 🙂