To dream that you are a Bridesmaid connotes an approaching sentiment. Likewise consider the familiar maxim "dependably a bridesmaid, never a lady of the hour". You could express your yearning to be in a conferred relationship."

To dream that you are a bridesmaid signifies a looming romance. Also consider the old adage "always a bridesmaid, never a bride". You could be expressing your desire to be in a committed relationship.