If she has a degree from Slovakia, going to law school in the US will be difficult. Her transcript will have to be assessed by LSAC and they will give it a score which is descriptive, not numerical. eg superior, above average, average etc. Even with a superior score, a degree from Slovakia will make it very difficult to gain admission to a US law school.
In addition law school is just as expensive as an undergraduate degree (around $300K by the time she goes). However, there are large scholarships, including full rides available for students that the institution deems desirable. Again, those free rides are going to be difficult to get with a degree from Slovakia. If she goes to Slovakia, she will be hampering her ability to get in and pay for law school.
If she gets a law degree from Slovakia and wishes to return to the US and practice law, she will have to pass the bar in her US state. Passing the bar without the instruction in US law will be difficult. But, there are other administrative hoops to jump through as well, which can take a lot of time. She may have a great degree of difficulty getting hired with a non-US degree.