This is really a long-shot, but I would go to this Egyptian government website
http://www.egypt.gov.eg/general/contact_us.aspx, click on "English" at the top left, set Destination: E-Government and Service Type: Submit Complaint or Inquery.
I would then ask, "My grandmother was Ivonna Rabezzana, born Cairo Egypt of Italian parents in 1900. Is it possible to obtain a copy of her birth certificate in English or multilingual format?"
How long were they in Egypt? Was she born there during a short visit, or were her parents actually residing in Egypt?
By the way, Lago
del Mucrone is a lake in Provincia di Biella in Regione Piemonte. Provincia di Biella contains 82 comuni, so you are going to have to narrow things down a bit before you have any hope of locating records (which are kept at the comune-level in Italy).
I think an Eygyptian birth certificate is your best bet on the hope that it will list her parent's place of birth or residence.