If you're struggling to find one big WOW present, you could always make her a 'bundle' with lots of small presents.
If she's really into Kpop, it should be pretty easy. All you need to do is get her posters, stickers, a tshirt or any other merchandise associated with her favorite kpop idols.
And there's really no end to the kind of stuff you can buy; everything from Super Junior backpacks through to Big Bang socks!