If she is there for limited time then it is better she just visits an Apple store and gets an unlocked version of the phone. iPhone 5 she probably wont be able to get in Apple stores since that is discontinued now. 4S will be available.
So the idea of buying from the US is that its cheaper than buying in india. Why don't you tell her to go for a 5s. if she can afford a 5 then she can find whatever extra to get a 5s.
How does warranty work with Apple. International like Asus or not.