Green’s Dictionary of Slang

(US) a servant, a working girl, the assumption is of promiscuity or sexual availability.

1841		Sun. Flash (NY) 17 Oct. n.p.: The latter hypothesis is not to be entertained, as no ‘slewer’ could be expected to possess such speed.
1842		Whip & Satirist of NY & Brooklyn 5 Mar. n.p.: It is at once a house of assignation, a brothel, and [...] a house fo seduction [...] Here the humble pot-slewer and the more dashing semptress may always find a ready customer.
1842		Wkly Rake (NY) 18 June n.p.: the rake advises [...] K.V. to support his family decently, and not keep company with ‘slewers’ .
1845		Gleaner (Manchester, NH) 4 Oct. n.p.: Certain biddies and pot-slewers of Pine, Chestnut and several other streets.
1856		Life in Boston & N.Y. (Boston, MA) 11 Oct. n.p.: She was formerly a pot-slewer in a nameless edifice.