If Air Force is mentioned in the lor, then there's no need to update them. As for changing her mind and only wanting Air Force, that too is not a big deal. One thing I've learned in the last 40 years about myself and young teens, is while they may not always know what they want for their future, they are pretty good and determining what it is they DON'T want.
I've never been a fan of the philosophy of applying to ALL the academies. The position to apply to all the academies usually comes from the position of looking at it from a free college education perspective. That's fine if you are looking at applying to multiple traditional universities. If you can apply for multiple scholarships at multiple schools, that is understandable. But military academies are more than a free education. There is a minimum of a 9 year commitment to that lifestyle. 4 at the academy and 5 on active duty. Applicants really need to consider what it is they want for their future. Sometimes the decision might need to be based instead on what they don't want. Especially if they are unsure of what they do want. And parents have to remember that this isn't their life. It's their child's life and future. The child has to make this decision.
The best thing is to help your child figure out what they want for their future. Or, at least what they don't want. When my son applied to the academy, he had decided that he wanted an Air Force career. Or at least for a little while. As such, h only applied to the Air Force academy. He figured, that if he wasn't accepted, he would apply also to ROTC. He may not have known 100% what he wanted, but he knew what he didn't want. Now, whether he stays in the Air Force for 20+ years or gets out at 12, only he will decide. Every day, he creates new options for that future decision. He graduated the academy in 2012. He's now a captain with his b.s., m.s. And PhD. But that doesn't mean that his future is totally written in stone. He's had his mind change a number of times over the last 8 years. And it will change more times in the future. It will probably change again when he's done with training and is doing his real Air Force job. Probably again when he gets married.
The point is, it is his life. He has to make the decisions. If he didn't see himself in the army or navy, then he shouldn't apply for those academies. And neither should your child. The military academies aren't their only option. If a child is good enough to get into an academy, then there's a 90% chance that they can get into just about any college or university in the country. Help them discover what they want. Or at least, what they don't want. And support them in their endeavors. The best way is to ask them..... If money wasn't important, and which school you attended wasn't important, and all that is important is that you're doing what you want is, ..... Then what is it you'd like to do? There are some kids that really truly want a military career. Very few think it doesn't matter which branch of service. Some want the military as a stepping stone to something else. Many that I've interviewed, weren't even sure that the military was even what they wanted. For them, it was simply another option. And of course, many parents, friends, and relatives are influential in their decisions.
The bottom line is, it's your child's life, it's your child's decision. It's good to help them understand all their options, pros, cons, etc. but help them figure out what they want, or at the least what they don't want, and support them in trying to attain that goal. I've seen a lot of young people accept opportunities to military academies or traditional schools that they weren't really thrilled about. They weren't happy. I've also seen kids who knew what they wanted and turn down offers to prestigious schools and attend the local university of whatever because that's what they wanted; and they were happy and succeeded. I know it is difficult, but it's your child's life, it's your child's decision.