Just go with the flow, taking care to both nuture and naturally play through the situation.
Try to roleplay your character as to how you think he'd respond to Viconia's emotionally charged interrogations, rather than try to simply pre-judge her responses and manipulate her into a course of action.
Viconia is a very well written complex character and I definitely enjoyed having her in my party from both BG1-2/ToB. Hearing her romance theme from BGII gives me the chills when I listen to it on the soundtrack!
Although my true neutral druid Vigamortis and her were eventually physically entwined, the relationship was doomed to fail and she ended it. In a fit of betrayed and jealous rage, Vigamortis ended up cheating on Viconia in the Underdark!
Yet somehow the depth of their experiences together kept her in the party for the rest of the game and Throne of Bhaal. I don't recall any further changes in the relationship however after it became 'platonic'. [img]smile.gif[/img]
I might have to try the Aerie romance one day, but I can't see it being half as fascinating as ol' Vick.