The heartbreak ends the relationship, not idea what she says I never had the heart to make Cassandra sad. I almost have heart attacks when I see Cassandra's disapprove actually.
The inquisitor says "If you're Divine, then there is no room for us" to which she responds "I wish it were otherwise". The only other difference is the "I could be named Divine any day soon & you will be pulled in a hundred different directions." & the rest of the romance ending is the same.
I chose the "I'm happy for you" option where the inquisitor says something like "That's wonderful news, you will make an excellent Divine" & Cass responds "I'm glad you believe so"
An ignorant inquisitor is a happy inquisitor!
Play it cool & remain in Denial 
The reason's I elected Cassandra for the position is IMO because this is the greatest opportunity for her to kick ass take names & reform southern Thedas in her image, which I trust because she has a good heart & Balls of Steel.
Also because it ads some drama to the Romance, where duty & religion comes between two people who love each other.
Will they continue their relationship in secret?
Will they be together some day when duty no longer separates them & the world no longer needs them?
Or will they throw themselves at whatever world ending problem demands their attention next so they can't pine too long over their lost love, less these thoughts turn them bitter at the world they gave up their happiness to serve?
Think of the Potential! Think of the Feels! 
Whatever happens, I'm going down with this ship 