Private schools are more conversational than literary/grammar oriented, so not being an expert in the language isn't a major hurdle.
Having taught in Asia for 3+ years, I'd advise your niece to study different countries and their culture before making a decision. Read some the country's magazines and on-line websites as well as novels...and watch some movies...sometimes fiction is truer than fact.
Countries on any one continent are not all the same. It takes a good 6 months to get used to living with a different set of rules and social expectations (not to mention a different language), so I'd recommend a stay of at least 2 years. She should also take side trips to neighboring countries and see how different they are.