At least in 13 Going on 30, *SPOILER ALERT* he marries the fiancee first. Then Jenna wishes herself back in time and then she and Matty get married, after they fast-forward in time, of course. Anyone confused?
Oh, and there is While You Were Sleeping in which she was only fake engaged to the first guy before she fell in love with his brother.
Still, I plan on getting married to my fiance. Whoever he is. Being LDS does reduce the chances of me getting married to the bartender at least.
As they say in The Holiday, you should be the lead in your own life, right? That's definitely my intention. Even if I look a little more like Nia Vardalos than Kate Hudson, they're both gorgeous.