I don't know how many of you found the ViVi interactions as she is not listed in the Wiki but try to go to her wearing Glace ; )
Not sure why does this matter if Celica is in her body or not for this?
But I specifically reference a spicy cutscene that happens (and is not saved in the dream world) where if you wear glace and you still have control, you can increase the Vivi relationship if you talk to her and she helps Glace take control over you.