What @happy1 said. With the exception of a few areas (where direct admit to major is required) the whole point of the US collegiate system is that students get to taste test what subjects are like at university level.
It’s also a time when maturing/brain development is going full steam, and whole new ideas can come out of nowhere. As an example, a niece who had been IR-focused all through HS, got into a college famous for IR, took intro IR with the famous, beloved prof…and discovered it was not at all interesting to her as a field. She was also taking a science class to meet a distribution requirement and fell in love with the field and is now happily finishing a PhD in molecular biology. Nobody saw that coming! It works the other way also: there is a woman well known in the foreign policy world who started college as a classics major, but took an IR course to meet distribution requirements. Her teacher was a then-unknown Condoleeza Rice, and she ended up having to finish grad school in DC b/c she was working in the WH by then.
@aquapt’s points are also spot-on, both on the current emphasis on data analytics and on the need for grad school. If she stays in that general sphere (whether law / public policy / etc), 1) a bunch of poorly-stipended internships and insultingly basic entry level jobs and 2) expensive grad school are in her future. The data analytics part will improve #1 somewhat, but unless she’s crackerjack at it, it won’t obviate the need for #2, probably 3-5 years after college.
What you can do for her now and going forward is to help her not have debt, which will enable her to take the early stage internships & entry level jobs and still keep bread on the table. Grad school in any of these fields is shockingly expensive.
A fancy-name private school is not mission-critical. What will matter is the resume she builds in college- esp the internships. Pretty much every uni has a DC semester and study abroad options. All of the major PP orgs (public and private) have internships which are advertised online. State Us can take her wherever she wants to go: a different niece went to a very ordinary State U, and ended up with a Truman Fellowship, which paid for Harvard Law School.
tl;dr: Seriously: at this stage she doesn’t need you to be scouting majors for her. This truly needs to be her following the path of her interests and seeing where it leads. Your part will come as you listen to her weighing the pros and cons of different options and ask open-ended questions to help her clarify her thinking.