This is the 12576th most frequent Polish word.
narzeczona
"Narzeczona" means "fiancée" (a woman engaged to be married).
In this sentence, 'narzeczona' refers to a woman who is engaged to be married to the speaker, emphasizing her role in the wedding planning.
Moja narzeczona planuje nasze wesele.
My fiancée is planning our wedding.
Here, 'narzeczona' is used to denote the fiancée of the speaker's brother, illustrating a relationship to another family member.
Narzeczona mojego brata jest bardzo sympatyczna.
My brother's fiancée is very kind.
In this context, 'narzeczoną' is in the accusative case and refers to the woman being asked to accept an engagement proposal from a man.