Why avoid the obvious? The master wraith chooses the one person who can create most doubt in the NPC, and for Solaufein, esp. Weimer's Solaufein, that's definitely Phaere. In any other case, I for one would be left wondering "Hm? Why not Phaere?"
The dialogue could check which of the Phaere talks with Sola have already taken place and how Charname reacted, i.e. does Solaufein still feel guilty for her death, or has he come to terms with it, and by what reasons?
To wake these doubts again, i.e. whether Phaere could have been saved, and whether Solaufein was right in betraying her, and whether the death of some people (Phaere and Ardulace) is a reasonable price for the life of many (the ones that would have died in the war) - that would be what I would expect from the Wraith.
If Wes already has a Master Wraith dialogue... does he read this Workshop board now and then?