You can refer to a woman as the 'bride' before the wedding. Provided the wedding is in the process of being planned, she is already the 'bride' as regards the wedding plans (and her intended is the '(bride)groom').
And you can be someone's fiancée without actually having made any wedding arrangements. Some people get engaged years before making any actual plans to get wed.
I agree that it is not unusual to use "fiancée" to describe a long-term relationship, but I would call it a euphemism. There is the strong connotation in the word "fiancée" that there is an intention to get married.