the Mindi Buttons site is the real Miranda as is MindiButtons on Twitter. (it's linked to by several important people in the theatre industry, which wouldn't be the case for a faker) Miranda's graduating from University of Melbourne as mentioned on the Mindi Buttons site is easily verifiable (she's mentioned here
at the UniMelb site).
Miranda is also mentioned here
as having been nominated for a musical theatre guild award while living in Australia.