There is East Greta Junction, which is the start of the mostly coal-hauling South Maitland Railway Pty Ltd.
There is also Greta station on the Great Northern Line, which may or may not have had sidings for coal traffic.
The whole coalfield might even be called the Greta Coalfield.
Since the SMR came first (by 100 years or more) in the scheme of things, if there is a conflict between Greta T. and her namesake, then Greta T. the anti-coal environmentalist is the one who has to change her name. What do others think?