Most OP princesses only develop the character progression from liking Luffy to wanking him off. Whilst Pudding goes from lying to herself about her feelings, to truly wanting to do what she wants and knowing herself. She went from "hating" Sanji, to falling in love with him.
Sure Viola had the same shit happen to her. But she was truly always good. Pudding was a villain princess that betrayed her family because of the kindness showed to her which no one has done.
Thus Pudding is the only princess that is actually complex and interesting. Fighting over her loyalty to her family which treats her bad in comparison to a stranger that shows her no kindness. The duality between whether she is truly doing the right thing or wrong, makes her develop a split personality. Both of the things she says are both her true feelings, yet she cant control and hide herself after Sanji told her to be true to herself. Only when Sanji was about to leave, did she realise that she did the right thing and thanks him for finally letting her find herself.