I think it’s very difficult to approach this from the standpoint of viewing her talent, as a non-major participant in musical theater, as a “hook” to achieve a desirable and affordable acceptance. That’s going to be tough, because for the most part, schools that aren’t invested enough in MT to have a strong and competitive program, aren’t going to be invested enough to recruit her for her talent, either.
I think that on the first pass, I’d take the theater piece out of the equation and just ask, where could she study what she wants, for a price you can afford, in an environment she would like and with as strong an academic reputation as possible? Once you have a list, then see what the theater opportunities look like and where she might find fit in that respect.
She has good course rigor, and her grades and scores aren’t bad. The problem is that her record isn’t quite strong enough to score big merit at competitive schools. (Also, I’m not clear whether you would qualify for need-based aid, but the most generous schools that meet need are also not going to be in range. But that doesn’t mean need-based aid can’t be part of the picture. As others have said, run the Net Price Calculators for schools that have already been suggested - do some look affordable?)
There are some private colleges that have Flagship Match rates that would make them affordable. Hendrix is one, for example, and it has an IR major. (And of course psychology - pretty much every college has a psych major.) International Relations & Global Studies | Hendrix College Theater looks pretty non-musical there, though. Another flagship-match school is Oglethorpe, in Atlanta. This would give her major-city access, with lots of the desired internship opportunities, etc. And the theater piece is interesting, because they have a long-standing collaboration with a nonprofit MT group, and put on joint productions in which both Oglethorpe and community actors perform. (Students cast in Actor's Express co-production of "Everybody's Talking About Jamie" - The Source) They have psych and intl studies, and they’re also in the Atlanta consortium with heavy-hitter schools like Emory and Georgia Tech (which has a particularly strong IR program - cross-registering there could be a big enhancement).
IR-wise, is she interested in a particular part of the world?
Trinity U in San Antonio might be another school to run the NPC for. https://www.trinity.edu/academics/cosb/iter/international-studies-ba
U of Houston could be a more attractive option if she could make it into the Honors College. Based on the profile, this seems like a little bit of a stretch but not necessarily out of the question: Honors Profile - University of Houston
Given her interest in IR but the relative weakness of her foreign language background, one path to consider might be a gap year abroad - living with a host family and doing an extra year of high school in the host country - through AFS or a similar organization. This would give her a massive leap in language skills, and establish her seriousness about an international focus. Plus, she could add some additional AP-level coursework, and include her senior-year courses and grades in her GPA as an applicant. Would she be interested in that sort of experience?