In "Berenice" by Edgar Allan Poe, is Berenice really dead, or is she alive? Is she in a state like a zombie?

The narrator describes a "disease" which fell upon Berenice. He says that the disease caused "a spirit of change" to sweep over her, and that this "spirit" pervaded "her mind, her habits, and her character." He also says that the disease "came and went," implying that it did not kill her. This impression is compounded when the narrator says that after the disease went, he "knew her [Berenice] not—or no longer as Berenice." Thus it seems that while the disease did not kill Berenice, it did transform her into a different person, a person that would not have been recognized as the lively Berenice who existed before the disease.
On the other hand, if the Berenice that existed after the disease was essentially a different Berenice to the one that existed before the disease, then it would be correct, in a sense, to say that the disease killed the original Berenice. Perhaps this is why the narrator describes the disease as "a fatal disease."
The Berenice that exists after the disease suffers from a sort of epilepsy, which puts her into a "trance very nearly resembling positive dissolution." The narrator later describes this same Berenice "not as the living and breathing Berenice but as the Berenice of a dream." The Berenice of these descriptions does seem somewhat like a zombie. She seems lifeless, especially when compared to the Berenice that existed before the disease.
Later in the story, the zombie-like Berenice dies after a particularly violent epileptic fit. She then comes back to life and is described as "a disfigured body . . . a body enshrouded, yet still breathing, still palpitating, still alive!" The phrase, "still breathing" implies perhaps a zombie rather than the more conventional ghost. At this point, it is probably correct to say that she certainly isn't, in any meaningful sense of the word, dead. And it is probably just as correct to say that she does exist in something like a zombie state.