DD is using USAFA's workout from the admissions page. It's a progressive workout that begins 12 weeks out from BCT. You can pick it up at any point. She is not an athlete, per se. She's finding it very helpful.
She also works out with the Marines every Monday night. The Marine workout is to prepare new recruits for their boot camp. She is pushed to her max with them and they give her no mercy.
I think both of these will help her, but I'm not sure anything can totally prepare a person for BCT.