D is on track for a BS in a Physics with an Astrophysics focus, but won’t have time to add a minor in Geology. She can take the basic Geology courses and maybe one or two Geology electives.
Will she have any problem getting into a MS program for Geology? She is interested and has done research in planetary geology.
As long as she takes some geology classes, even if there’s no minor, it should be okay.
If she wants, she could also look into geophysics–most MS geophysics programs seem to prefer taking on people with a BS in physics, and then teaching them the geology part of it once they get in (as opposed to teaching physics to geology students.)
fyi, the graduate school forum is very useful for questions like this.
Also don’t hesitate to read the pages of various geology programs. U of Michigan says
“Students holding a BS, BA, or MS degree in any field of science are encouraged to apply to the PhD program. Financial support is guaranteed for all PhD students who enroll.”
and you are granted a MS on the way to the PHD if you want. Additionally she could discuss this with someone in the Geology dept, profs are good resources for talking about grad school admissions, as are grad students sometimes.