Vivienne is a fantastic character. She's my favorite companion of the entire series. She's witty and confident, yet a little vulnerable. I could watch her troll the other companions for hours and not get bored. If you friend-path her, she becomes a close confidant and ally. I absolutely adore this woman. She's a touch too conservative for me with her stance on the mage/templar rebellion, but she has never held that against me outside of a few disapproval points. I think that her writer (was it Mary?) knocked it out of the park with her. And Indira Varma sealed the deal with a stellar bit of acting.
Well, she hated me for it to the point of rearranging furniture for some reason.
Personally, I can barely stand looking at her or listening to her. The only banter I ever want to hear from her is with Cole, and that's because of how quickly Cole cuts through her defenses while being impossible to troll. Indira Varma was a good VA, but was good at creating someone I'd rather drill my eardrums out than hear again.