You can report the theft to law enforcement in the jurisdiction where it occurred and see what, if anything, they can do for you. You didn't identify any U.S. state, or even any nation -- and laws vary by nation. If this act of theft occurred "overseas", which I infer to mean "not in the United States", then U.S. legal authorities may not view it as their problem, or may be of limited assistance due to the fact that your ex- lives in another country.

If you want to sue her, assuming she has any money, you are likely best served by suing her in her present nation of residence. You may be able to sue in the U.S. (assuming that's where you are located, and that's where the loans were made), but your ex- will have jurisdictional objections to at least some of the claims (e.g., claims relating to loans or acts that occurred after you and she relocated overseas), plus your ex- will be able to object to the enforcement of the U.S. judgment in her nation -- or may be in a nation that won't even enforce a U.S. money judgment.

If you believe that you have a chance of recovering money from her, talk to a lawyer in the nation in which she is presently living about the cost of litigation and your chances of success.