As would probably be the case with any person, it depends on the person~ ^^ Are you able to provide more detail on why you're looking to purchase a gift?

Hmmm...if you're close friends, maybe something that will remind her of all the memories you made while she was with you? Something from your hometown or a book of pictures.

I think it's less important that they're Korean and more important that they're themselves. It depends on their individual interests