To quote Mary Kirby from her interview on Vivienne, :- "So she resorts to the only logical course of action for a courtier: she throws a party for them."
Vivienne appears to be a mage-politician. While that makes her powerful in many ways, it is something one who wishes to approach and communicate with her must keep in mind.
As such, I am of the opinion that one should deal with Vivienne the way they would treat a powerful politician.
When it comes to politics and politicians, I usually look to House of Cards to see how they operate and function. Vivienne, working in the Orlesian court, where the Great Game is played at the highest levels with the highest stakes, is in fact no different than an American politician in the U.S.A Congress.
Which means that I would not trust her. Not because I do not like but her nature of her work, which is a politician, automatically makes her untrustworthy.
Here is an excerpt from the World of Thedas by Leliana :- "As a bard, you are welcome anywhere in Orlais. Doors are opened to you with generous smiles, their wearers confident that no one would falsely pretend to such a title for fear of retribution. Your slightest request is immediately seen to. Your services are expensive and yet actively sought, and those who cannot afford them beg only to not have your displeasure turn their way.
One day, however, you will awaken. You will realize the smiles are false, and behind them lies revenge. At the first moment of weakness, your brother and sister bards will be unleashed upon you like a pack of hounds, and you will realize they are not your brothers and sisters at all. For all your fancy intrigue, you have spent your life creating nothing of worth. You have been swallowed by the web of your own deceits, and the Game of which you believed yourself master? It moves on without you, uncaring."
Granted, Vivienne is not a bard, she is a mage. However, from the description of the Great Game, no one in their right mind will trust the people who play it.
My Inquisitors would be like this towards Vivienne :- "So, you are an Orlesian courtier and you are a powerful mage ? Okay, good to have you with us. However, I will not completely trust you. You don't just simply trust those who play the Game, especially at your level, First Enchanter."