Green’s Dictionary of Slang

1. (UK Und.) a low-grade prostitute.

1846

Swell’s Night Guide 74: [A] variety of tail pieces of all sizes and complexion from the flash mots of Dover-street, [...] and the drabs of Windmill-street, lashers of Cornwall-road.

2. (Irish) an attractive woman, a beauty.

1991		T. Delaney Where We Sported and Played 662: Some of the women were right lashers.
1993		M. Verdon Shawlies, Echo Boys, the Marsh and the Lanes 35: Whacker Murphy went shifting in the Arc and clicked a dolly from Gurrane. She was a lasher with a pair of josies that would act as buffers for the Innisfallen.
2005		P. Howard Curious Incident of the Dog in the Nightdress 102: Medb turns out to be a lasher.
2015		L. McInerney Glorious Heresies 80: He thought I was a lasher and I didn’t deny him the chance to keep telling me.