In a recent game of 10th level characters, we had a small issue in the group. To set the scene, my character was a serpentfolk witch, specializing in enchantment and specifically mind-magic. We had a were-tiger barbarian, a half-dragon bugbear paladin (worshiped Apsu the Waybringer), and a dark stalker rogue. (It was a monster campaign, in case that wasn't obvious).
Well, the focus of the campaign was supposed to be monstrous entities overcoming social taboos in order to aid a kingdom from a threat that only they would have the power to overcome. The problem was, while the majority of the group was good-aligned, the barbarian was chaotic neutral.
My character, on the other hand, was lawful good, and worshipped Abadar. Specifically, being raised in a caste-system, he was of the belief that the most good came from conforming to the law.
So, when the chaotic barbarian continuously thwarted our attempts to negotiate with the local royalty (with the gods on high who had bid us to complete the mission continuously saying that All of Us were needed) I decided to dominate her.
It worked. She stopped being chaotic, at least at the times we needed her to be. Also, having no knowledge of spellcasting, she had no idea it was me who had done it. The game continued, the GM agreed that it was within reason for my character to do this, and everyone had fun.
Except her. She got horribly upset, claiming that she should be the only one who can control her character, and that if she wants to be chaotic then she should be allowed to. No one disagreed, because we play that the player has complete control of the character, so long as the player can give some kind of reason why the character would act that way (which only really prevents characters from acting completely insane.)
So, here's my question; Was what I did wrong? I broke no rules, no one else in the group blames me (except her, and she's less mad at me and more mad at the DM for letting me do it) and I never abused the ability. All I did was keep her from being chaotic at important moments.
To put it another way: Is controlling another player's character, specifically through rules allowed in the game, acceptable behavior?