Money: the laundering of. That's Harlem's speciality and that's what makes her invaluable to the Sirens and other members of New Bridgeport's criminal element. After all, at the end of a long, hard day of drug dealing, counterfeiting, dragon trafficking, and Moons knows what else, the money that a Pyrrhian gang brings in is still as shady as heck. After all, it can't be spent without the authorities getting suspicious and asking awkward questions - like where did that ten thousand dollars come from? Without a money launderer to clean it up, dirty cash is basically useless.
That's where Harlem comes in. She takes the gangs' dirty money and converts it into nice, clean, scrupulously legal cash flow. The process involves overreporting the Bagel hotel and its casino's income, in order to mix the dirty money with legitimate revenue. Thanks to loose record-keeping and New Bridgeport's signature lack of oversight, Harlem and the bookkeepers at the Bagel have been getting away with it for a pretty long time.
But she's a dragoness of many talents, and her other major talent is art (forgery). Harlem is actually quite good with a brush and paints. How good? Good enough to mimic the styles of the great Pyrrhian masters, good enough to pass her works off as worth a few hundred thousand dollars. It's really a shame that she wasn't able to make a name for herself as an up-and-coming artist upon graduating college, and instead turned to more profitable and more illegal ventures. Nowadays Harlem has a small studio tucked away in her suite in the Bagel Hotel. She finds painting therapeutic, though because of her other duties she doesn't have much time to do it.
Harlem's other hobby of sorts is to go down into the Bagel Hotel's casino and deal cards for a bit, even though it's beneath her station.