I was wondering if she got some of her money following her father's death. The house she inherited from her mother, split with her sister, wouldn't have funded all her property purchases. Perhaps her mother left a large cash inheritance as well. But if she'd inherited from her father a decade before, it's more likely that her husband would have entitlement.
It's unclear exactly how big her property portfolio really is. There are a couple of articles that paint her as a mini-tycoon, but I'm not sure that's the reality.
From this Daily Mail article:
Following her mother's death, Erin sold her mother's home for $900K. Presumably this was split with her sister.
She then bought a home in Korumburra and sold it within seven months. (This is the home with the drawings on the wall.) The article states she made $85K in profit. But if the market in Australia is anything like the one in the U.S., she probably at best broke even after closing costs, sales commissions, fees, etc.
She also bought land in Leongatha for $260K and built the house where the fateful lunch took place. According to the Mail, she owns this home 'outright'. The Mail also describes this as place as currently worth a million dollars, but if so this must have been a very expensive house build.
Her other home is in Mount Waverley, the town where she claimed to have bought the dried mushrooms from an Asian store. She purchased it for $931K around the same time she bought the land in Leongatha. Unlike the other property, this one is not described as being owned outright. Possibly she holds a mortgage on it.
So, depending on the valuations and mortgages she holds on her homes, I could see her actual property portfolio ranging from around 750K to over 2 million.