Why does she need to be, and pardon the expression, but "Super Whore"?
In fact, wouldn't it be more interesting if she was an average woman with tens across (or similar)?
I mean we're sitting here "optimizing" a hooker while entirely ignoring the actual character we're talking about.
First, in the grand scheme of things few and far between are those who could make a living alternatively still selling their body for relations. If someone is engaged in routinely exchanging their intimacy for money you can rest assured it's because they didn't have a lot of options to begin with.
Having a hard time grasping what I'm talking about? Can you picture Superman selling it on the corner after the bars let out? Why not?
A "whore" that does have significant abilities is more likely fighting for a cause of some sort and would use whore (or whorish behavior) as a cover. A spy for example (See: Clear and Present Danger's Felix Cortez).
The question then becomes one of what's this NPCs purpose? If they're a hooker and are fighting for the group then why aren't they getting their share of the spoils? At that point they're either the world's dumbest sex worker or a slave.
And if they're a slave, especially a sex slave just call it for what it is rather than "whore".
If the NPC is really just there to provide sexual relief to a paying customer there's slim to no reason for them to have extraordinary abilities and in fact may become a much more valuable storytelling tool if they are just a regular person.
There's a variety of angles that can be found in the (and I'm just going to assume it's a she at this point because I believe that's what was indicated as desired)... found in the "She's just an ordinary woman" hook.
Examples include...
Organizations and individuals that view what the player is doing as truly wrong and view them as an enemy.
The view that the "whore" would fall into love... or absolute hate for the player character.
The question of pregnancy is always a fascinating one... especially if the PC is somehow extraordinary.
The understanding of how the player character treats the NPC and the effects of that treatment. If she' treated terribly but feels there's no other life for her does she simply suicide? Does she engage in other rash and risky behavior? If she's treated well (but still hates her "master") does she one day decide to stop plying her body for cash, steal the player's magic shield and run off into the night? If so, what do the PCs do?
If she's extraordinary she'll have less motivation to actually *do* something about her situation because she has a built in motivation to keep doing whatever it is she's doing. If she can dominate someone once per week you can bet your ass she's not going to be turning tricks by the waterfront. And even if she's somehow terribly impressive the only way you'd get someone like that is through an immense expenditure of cash... at which point she'd flee and set up a coffee shop or something.