Wow, this is going two separate ways. I'm actually seeing more than a single instance here; the immediate issue is one of character portraits; there's the chance (however slight) that the player does, in fact, 'get it' and is now needling the DM (Don) out of basic spite. Proof positive: just because it's female & rolls dice, doesn't mean you want to date it. That aside.
We're talking in an apples to oranges comparison if the issue with the character portrait matters. You say "This is." She says "It ain't." The resolution here is to either sit down, one on one, and have print outs for purposes of reference and ask (thus turning the problem around) why none of these work for her, when she selected the racial package after having it made utterly clear what that package means and what it entails. It sounds, in part, like you're on the defensive. Force her to justify her actions. "You can have the ball back, when you explain, in clear, simple detail, why I should give it to you."
Failing that, or if she decides (and has failed to articulate; some people have difficulty converting what they think or feel into what they say, or what they want) that when you said 'Dark Elf' she heard 'Drow,' then you've at least resolved the immediate issue at hand, i.e., why Dark-Skinned Elves aren't working and she wants a white-haired, black/purple skinned Elf. From there it's a simple matter of either changing the package, or making the cosmetic adjustment. And, if you're clever, you can always let said adjustment (from brown to purple) be incredibly detrimental. People recognize Drow, people kill Drow. Congratulations! Your arguments have made you a victim!
Second: never, ever keep a player because you feel an obligation. The larger issue here is one of improper behavior in your world, for your genre, for your campaign. Make sure she's clear on the rules (yes, she can shoot into a dark room without penalties, if she has ambient light, if her target doesn't have cover or concealment, etc.) and not simply abusing them for the sake of abusing them. Most players, given enough books, will start generating combos that maximize their potential. That, in and of itself, isn't wrong. Trying to change the rules to fit their circumstances, that's wrong.
Flip side: this is a game. Game. Even as a die-hard story teller, I recognize there are times that without bending a little, I can't get what I want, which is to tell my story in a cooperative, dynamic setting. You can give a player what they want without hamstrining yourself. If you need a mediator (generally the DM is the mediator) then you may want to approach her husband first, explain your concerns, and instead of asking "Are you on my side, or hers" which is a tremendous mistake, ask him to approach it impartially. "She has a point I can't understand, and it's making me running this game, which you enjoy and are involved in, difficult. Please help me bridge the gap to fix this problem so we can go back to playing."
Good luck.
