I hope she’s ready to affirm same-sex marriage. (that’s a requirement now)
ROTC. Pick a service, then find a good university with the ROTC program leading to a commission in the service she chooses. Most importantly, become an officer. There is nothing dishonorable about serving enlisted but life for an officer is very much better.
I hope she’s prepared to witness some of the most grotesque hypocrisy and double-standards a person can see in adult life.
Hand her a pocket copy of the Constitution and ask her to read it carefully, so she understands just what it is she’s swearing to give her life to defense. That will put her in a league of her own in the military these days (because most current military officers have absolutely no idea).