My girlfriend gets angry at me because I'm preparing for the worst. Who's right on this?

My girlfriend and I are both 17. We've been dating for the longest time and have spent all our adolescence together. We are so madly in love that we want to get married, but we decided to hold it off until we have graduated post-grads and have stabilized careers (I'm interested in either business or law). Recently we've been getting very serious, almost to an extreme. We've been discussing future jobs, schedules, possible workplaces, salaries, houses, cars, children, costs, loans, stocks, etc. Our plan is that she goes to the four years of college and I go to four years plus post grads, then we meet up again and wed. Just the other day though. I told her she should do post-grads, too, in case I die an early, sudden death or am permanently injured from an accident. She got really scared and told me not to say those things and pretend stuff like that doesn't happen. I don't like fighting with her so I kept it to myself. But then I realized vie had tons of plans and wills on what she should do should she be widowed young. She scolded me for being too pessimistic and creepy like that, but I thought it was a good idea to start preparing fir the future. Who do you think was in the right?