Currently it's impossible for an Arland Princess to achieve a Perfect ending even with NG+ bonuses due to Cato requiring 75+ manipulation. Could this change in the future?
I didn't get Cordelia's ending CG despite having maximum friendship with her, seeing all her scenes (save W2 Gazebo) and getting the best ending for Corval and Hise. Possibly because I married Lisle since she would normally marry him otherwise?