Possibly Japanese but definitely of east Asian origin. It has a contemporary setting (the '90s if not the Noughties) and tells the tale of a young woman co-existing as two different versions of herself, one straight-laced, the other more extroverted. Best way I can think to describe it is SLIDING DOORS meets THE MAN WHO HAUNTED HIMSELF.
ANN AND ANNA seems to be the closest I've come to remembering the title but an online search has returned bugger-all.
A Tale of Two Sisters?
Nope. It's sci fi at a stretch, definitely not horror.
Hanna Montana? ;)
V
Nope. It's sci fi at a stretch, definitely not horror.
Philistine
I'm intrigued now, but I need more details. Drama? Comedy? Kung fu? Anime? Is she the main character and does anything really nasty happen to her?
How about 2046? That's got various actresses appearing as different versions of the same characters.
This is your guy!
Anna & Anna (http://www.imdb.com/title/tt0985079/)
Coshtastic! Cheers, chum.