Hello. Just wanted to lay down a few thoughts from someone going through the same thing as the OP's DD. I will not pretend to have more experience with the military, or SA, or sacrifice. These are just my personal thoughts. I'm a senior in high school and have been honored with an appointment to USNA. It's been a goal I have been working towards since I learned about the Service Academies my sophomore year and I just about fell over when my Senator called to congratulate me.
Like your DD though, I began having doubts about my decision because I realized what a monumental move I was making. It took a lot of soul searching to isolate where these feelings were coming from. For me, I had two things that really were impacting my decision. First, was swimming. I am an avid, competitive swimmer and have talked to some DIII coaches through my college process. I love the athletic aspect, the team spirit, and the sport but sadly am too slow to swim at a DI level. This made me realize I was missing out on the "normal" college experience. When I went to a CVW, I was shocked that there were class periods and school bells of all things! I was looking forward to the freedom of college life on my own. Second, my graduation is in mid-June, making I-day a mere two weeks away from the end of my high school career. The swift turnaround from young high school student to shouting, "I do!" to an oath I would stand by for years to come gave me a small taste of the things I would sacrifice–time with friends and family, days on the beach, naps!
After some thought, I realized these were things I was willing to sacrifice if it meant helping others and keeping my country safe. I suggest your DD take the time to understand where her indecision comes from. For me, I was merely balking in the face of change.
It was a very introspective process. My parents tried to help by presented all my options (apply to civilian schools, SMCs, NROTC, continue with Navy) and reminded me that I have plenty of time to decide. They were supportive, but left the choice up to me. I'm very thankful that they did. As a fledging (and still utterly confused) adult, I need to be able to make my own decisions about my future. Personally, I believe you can show your DD the way, but if she needs to be re-inspired, it will have to come from her.
One last parting thought,
@6KDogwhistle. I don't think doubt equates to insincerity about commitment. I believe the doubt that OP's DD and I are facing, is from our understanding of the sacrifice and dedication that you brought up. We understand the consequences and want to test our resolve before we commit. I would rather experience this doubt and come out recommitted than continue on naive and only discovery my insecurity while at an academy.