… kidnapper (and her girlfriend)
She’s always one step behind the kidnapper and her girlfriend, sometimes it cuts to the kidnapped girlfriends point of view. At the end it’s revealed that the kidnapper and the girl searching for the kidnapper are the same person, just different personalities. That’s all I can remember but the movie was in color, and I think the protagonist was a blonde girl with short hair? It’s most likely PG-13 or R and made before 2010 at least.
High Tension (2003)? That’s the plot in a nutshell. But it’s strange that no mention is made of the extreme violence that ensues.