My advice? Just because you feel she's the one, that doesn't mean you have to get married right now. I've always had a personal rule since I was young enough to understand any aspect of relationships that I would date someone for at least a few years before getting married. So far, it's working
If she's the one, then there's no rush, and the more time you give to get to know eachother, then the more positive you will be by the time the time comes - far less pre-wedding jitters
Of course, this is also something that needs to be mutually understood. For example, onodrim knows very well that I will not get married until I've gone out with someone for 5 - absolute minimum, 3 - years and am 25/26. We've been going out for 4 years now and I'm goign to be 21 in a few months. I'd rather play it safe than sorry - and if this is someone I plan on spending the rest of my life with, I don't see why there should be a rush to get married. I have a whole lifetime