Someone... woah..... come on now... slllllowwwwwwwww down my friend. I know that love acn be very powerful when you are young. It was a while ago, but I was young once. You are still a child turning into a man. You need to give yourself time to mature and discover yourself. You need to discover yourself, who you are, and what you want before you can even consider what it is that you want from a life partner. You are placing WAY to much pressure on yourself and on this young lady. Relax, have fun together, date otehr people. Take the pressure off and you may find that you will spend even more time with her.
The facts are pretty clear .... people that marry young are much more likely to be divorced. It takes time to mature and figure out what you want. Not surprisingly people that wait until their late 20s to marry are more likley to have a long lasting marriage.
You may think this young lady is "the one". And, who knows, she may be. But, even if she is the one placing this much pressure on her will surely push her away. Back off. Be friends. If you enjoy each other's company a great friendship is a wonderful thing. Treasure that. But, be sure to date other people along the way. That is the only way you are going to know if you are making the correct choice for the rest of your life. Take the time and do it right.