I could almost see Vivienne hooking up with someone controversial for the sake of shock value, or to show other Game playing folk that they can't predict her future actions. She seems very intelligent-- I can't imagine she couldn't find SOME way to get an advantage out of whoever she was romancing. Could be a good bit of drama too-- confronting her about her motives for being with you. A romance with the Inquisitor evolving from pure politically convenience to truly held feelings? Lots of romantic potential there, I think.
That's what I think. I think she'd be like Morrigan, seducing him for personal gain until he cracks that icy shell. In Vivienne's case, instead of pregnancy, she likes to keep pretty things on her mantlepiece and likes to keep powerful pieces for The Game.
I feel like I'm describing her as a bit of a gold digger, but that's not quite what I'm trying to say. I doubt she walks into a room and makes a mental list of important people to bed, but if the inquisitor shows some interest, she might reciprocate because power. At first.