Parisian filles de maison

The number of filles de maison remained roughly the same during the last half of the century, but the number of tolerated and licensed houses decreased steadily. From 300 in 1840, the number declined to about 190 in 1860, to 128 in 1878, and to only 70 in 1886. Because the business expanded at the extreme ends of the social spectrum of brothel prostitution, the types of houses that remained in operation changed a great deal. Located for the most part between the exterior boulevards and the fortifications, houses of the most squalid variety, catering to the least elite customers, carried on and prospered. 

The second-rate houses almost disappeared, while the number of maisons de luxe (often called grandes tolerances) increased, mostly in proximity to the newly prosperous grands boulevards, the commercial centre of Paris, and particularly in the streets adjoining the Madeleine, the Bourse, and the Opera. During 1878, the year of an Exposition Universelle in Paris, establishments in the deluxe category doubled their earnings. 

Hollis Clayson painted Love.

Presumably, Mary Kelly didn't work at the lower end of the French market. She would have sold her gowns prior to her return to journey to London. So she worked upmarket and those few houses were registered.