One of the sub-genres of mystery fiction is that involving the plucky young woman who has the foresight to cast off the shackles that were keeping women at home, barefoot, pregnant and yada yada. Class barriers at this time were dissolving for many reasons, only one of which was the fact that an entire generation of Britain's young men had been wiped out and women were stepping in to fill the breaches. There were a few of these young ladies who cast off their pasts and leapt to the defense of the good guys, managing to get themselves close to the front lines of the war in France, either as ambulance drivers or nurses.
Phryne had not always been rich; she was actually born in Australia in circumstances of poverty, but her father came into an inheritance and the Fishers left their privation behind them. Phryne was named after a courtesan of extraordinary beauty who lived in Ancient Greece in the 4th century BC. This lovely was purported to be the model for some famous statues of Venus.