I seem to remember Jadzia becoming a "haughty bitch" in "You are Cordially Invited"...at least until Sisko took her down a few pegs.
Every woman has her moments when planning a wedding. And Jadzia's behavior during the wedding planning was really a symptom of her being a joined species. She was still thinking like Curzon when it came to Klingons and was used being treated with the respect that Curzon had earned. She wasn't used to being treated like her honor was unproven, which is why she had so much trouble with Sirella. Sirella didn't know or care about Curzon's history, only Jadzia's so that was a bit of a swerve. Plus she was marrying an alien.
Keiko didn't have the excuse of being a joined species with 7 lifetimes of memories. Nor was she marrying an alien, leading to culture clashes. She was a human married to a human. And she was a haughty bitch.