First, have you run the net price calculators on a few schools to make sure that you do not qualify for financial aid? Try a few state campuses and maybe a generous private school like Vandy. It’s pretty likely you’re correct since the formulas aren’t particularly generous with business owners, but run the numbers to make sure. Every college website is required to have a net price calculator somewhere so use the search function if it is not obvious.
And, once you have her PSAT and SAT test scores, you can look into merit aid as others have suggested.
If paying for an undergraduate degree is difficult, paying for law school may be even more so. Perhaps you should encourage her to explore other ways to serve the immigrant community besides as a lawyer?