EC, I don't have children, so I may be a bit biased. I'd support her wholeheartedly. I've prolly posted this elsewhere; last year I had the honor to spend some time on an Air Force Reserve base. I am still impressed with the professionalism, dedication, intelligence and courtesy displayed by the officers and enlisted people there. In fact, if I include the vets that I know, there is no other group that impresses me the same way.
Now is a time of danger for our service people. I understand your concern; however, so many of our young men and women want to do their part. Plus, if you support her now, she'll likely not fix her decision so much.
P.S. Thanks for serving in the world's most elite fighting force. (this is just my opinion and not a troll)