This may or may not answer your question but the words are derived from 17th- and 18th-century cant. A 'bunter' was originally a woman who collected rags and scraps of cloth in the street to peddle and/or pawn off for a living. At some point, it was expanded to include pickpockets and street thieves and came to be applied to any low-lived, vulgar woman more generally. So, it could literally just refer to a lower form of street-walker or it could be a term reserved for women who picked the pockets of their johns during or after servicing them.

As for 'bulk-monger', this too may be possibly connected to the idea of robbery as a 'bulk and file' referred to a pick-pocketing duo: the bulk distracted the mark while the file picked his pockets. That said, bulker was another term for street-walker and was generally reserved for those women who, by hard living and constant want, had completely lost whatever good looks they'd ever had. I'm confused about the 'monger' part though and I wonder if this is not some kind of reference to a low-tier prostitute with many children.

Sources: Richard Head, The canting academy, or, The Devils cabinet opened (London, 1673); Anonymous, A new canting dictionary: comprehending all the terms, antient and modern, used in the several tribes of gypsies, beggars, shoplifters, highwaymen, foot-pads, and all other clans of cheats… (London, 1725); Nathan Bailey, An universal etymological English dictionary (1721)

definitions from The Covent Garden Ladies: The Extraordinary Story of Harris's List:

bulk monger - a homeless prostitute who lives and plies her trade from the benches below shop fronts

bunter - a destitute prostitute