DonTadow said:
Her response
"shes having fun with it and wants to grow and see how far the relationships goes".
And that gives you something you can use. Inform her that she has to play the character according to the guidelines
she accepted, or else the choice will no longer be hers to make - the item will simply abandon her. Then, if she doesn't straighten up this aspect of her play, carry through on the threat.
I think your basic problem is that you have an unreformed munchkin on your hands (she's at the edge where power gamers become munchkins - if she was just inside the rules, she'd be a power gamer, but outside them she's a munchkin). The way to deal with a munchkin is to insist on an accurate and conservative interpretation of the rules in use in the campaign, and to religiously enforce role-playing disadvantages.
Mechanically, most of the power of a munchkin comes from creatively interpreting the rules of the game to her advantage. Hence the "I'm attacking an area, so it's a ranged touch attack, so there's no save." The thing is that it is the DM, not the player, who interprets the rules of the game. If something seems off
to you, don't allow it. But be sure to have reasons for disallowing something, and be sure to implement the rules fairly at all times. (Sadly, this increases the work you have to do. There's no way around that - you'll just need to suck it up.)
It is important, when dealing with a munchkin, that you not allow rules disputes to spill out of control at the game table. Make a ruling, allow a brief appeal, and either change your mind or go with your original choice. DO NOT allow further discussion of the matter during the game - if there's a problem it must be brought up later. Explain at the start of your next session that that's how things are going to be - you're making rulings to speed up the game, not to hurt players. (Be tactful when doing the above - what I've outlined is what I think you should do, but not necessarily the way you should do it. If you just declare that you've decided there will be no more rules arguments, you'll probably lose your players.)
As regards the roleplaying disadvantages, these are more difficult to implement. I suggest using a "three strikes and you're out" rule. Every time the player of a paladin greviously breaks his code of conduct because it's convenient, make a mark. Likewise for defying the edicts of this weapon. Once the character has two marks, warn the player that a fall is coming. Then, on the third strike, apply the penalty for breaking the restriction - a fall from grace, a loss of the item, or whatever.
The benefit of the "three strikes" thing is that the player can't complain they weren't warned, and the consequences are clear. Also, it won't be a sudden penalty - the punishment only comes after multiple problems. And by placing a number on it, you don't have to make a call that "enough is enough" - you have a clear threshold in your mind, and can simply count towards it.
Chances are that the player will whine anyway if you apply any sort of a penalty. She'll no doubt take the view that you're picking on her. This cannot be avoided. Just point out that you're not dealing with rules disputes during the session, and that she'll need to bring it up later.
She might walk over this. Honestly, I don't think that'll be a big loss. More troubling is that her husband might get angry, and if she walks then he'll probably walk. This, also, is too bad, but there's nothing you can do about it. One of the problems of dealing with couples is that a problem with one becomes a problem with both, and if she's a problem then it doesn't matter how good a player he is. The problem needs to be dealt with, and the consequences of that accepted. ThirdWizard is right: "Married folk count as one person."
