If you plan on going right to college then you ought to use that time to take college classes at your high school. They are ridiculously cheap. Even classes that don’t transfer as core credit to BYU still transfer as elective credit. And performing well in high school college classes will help her get into BYU. They will take into account if you have a 4.0 but your class rigor is very low.

And honestly high school college classes (especially concurrent enrollment) are easier than real college classes. So if she’s nervous about taking them I don’t see why she’d rather jump right into BYU.