A she dog, or doggess; the most offensive appellation that can be given to an English woman, even more provoking than that of whore, as may he gathered from the regular Billinsgate or St. Giles’s answer—“I may be a whore, but can’t be a bitch.”
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Bit * To BitchNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes