So, when did sham meet the Shark? after she became a thief in Purgatory, or before? if it was before it brings up the question of who the shark was and if he knew Maur before he was crippled. If Sham didn't meet the shark until after she became a thief then what is the connection between them?
I don't have any answers for you on this, but in my reading, it strikes me that it was probably a transitional thing. When she left the - what, palace? Castle? - ruling building complex, anyway, she wouldn't have instantly become a thief. I suspect the shark somehow found her, or she him, and they struck some kind of deal, he getting her training in the 'camouflage' she used, and ordinary lock picking, finding avenues of entry, what to look for, things like that, and she might have done some small mage workings for him. That's just a guess.
In the scene at the stables where the Shark meets the Reeve the Shark is really protective of Sham. Plus, she's one of the few who know a lot about him. this indicates a close relationship.
Why isn't sham one of his Whisper/ part of his gang? Because she doesn't want to be is my instinctive answer.
if anyone has speculation I'd love to hear it.
I think you're right, there. I doubt that in her most bacis identity, Sham thinks of herself as a thief. She's a mage, maybe a noble, a force of vengance for Maur, but not a thief for her own gain. She therefore wouldn't feel part of the Whisper underground.
They're flat out criminals, thieves, extortionists, blackmailers (note those two are different things!), pimps, whores, drug dealers, smugglers, bully-boys. They'll ply their trades among all, from the highest to the lowest. Sham only stole from high ranking invaders, as revenge and to care for Maur and herself.
