3 copies on Bodl but no mention of an Oyster girl, it's all about catching em and bringing em to port.

Here's the first verse of a freshly caught one FWIW

As I was rolling down the street,
A pretty lass I chanced to meet,
She fairly knocked me off me feet
A shouting of her wares.
    Oh oysters, sir, Oh oysters,
    Fresh oysters was her cry,
    They're freshly gathered from the bay,
    Me oysters won't you buy?