She suffered from "cancer", in fact a lymphoma, for four years, untreated as far as I can tell from her relatively uninformative website.
Lymphoma is an interesting form of cancer. If it is Hodgkin's lymphoma it is "one of the most curable cancers", and would be a medical travesty to allow it to go untreated.
https://www.nlm.nih.gov/medlineplus/ency/article/000580.htm
If it is non-Hodgkin lymphoma
http://m.cancer.org/cancer/non-hodgkinlymphoma/detailedguide/non-hodgkin-lymphoma-factors-prognosis
It would be more difficult, but still could have as high 91% survival at 5 yrs (with treatment).
She did receive treatment during hospitalization so her remission would not be spontaneous, or miraculous, just a successful medical treatment.
The fact that she had dreams and hallucinations during her hospitalization is not surprising. Claiming that these dreams represent a genuine experience of the afterlife on the other hand is unfounded assertion. Claiming that this experience resulted in her cure, while ignoring the role of her medical treatment in hospital is even more absurd.
Judging by her website she has a clear monetary incentive to persist in these claims, without providing any believable documentation, while taking advantage of the gullible.