Nowadays, we can treat it with anti viral medication such as Zovirax: the same medicine that is used for herpes. (chicken pox is a herpes type virus: Herpes Zoster. Herpes simplexI causes cold sores and Herpes simplex II causes genital herpes).
I suspect she had cancer, but was not aware she was that sick. Or maybe she was getting chemo and that ruined her immune system, but if she hadn't gotten chicken pox could have served a couple more years in congress.
Usually when varicella is this bad, it is associated with immunocompromise. Geriatric patients can be compromised in this fashion. Other diagnoses are purely speculative. I take on face value the comments from the politicians (that it was a case of varicella pneumonia). The fact we can read into this deeper was probably not intended by the Hawaii state Democratic Party.