Used as a hyperbolic expression referring to a woman’s walk after a large amount of sex or sex with a man with a large appendage.
“Wow, she’s hot. A night with me and she’ll be walking like John Wayne”
A bottle of leg-opener is Australian for wine. It’s well accepted that women are far more promiscuous after drinking lots of wine.
Give that Sheila a bottle of leg-opener and she’s good to go...