It is a psychological horror. I’ve watched it around 2001 and movie is probably shoot few years earlier.
The main character is a woman/girl in her twenties. I think she had semi-long dark hair. Complete movie is happening in the house which has only ground floor (from memory it kind of reminds me of one of those big brother’s houses). There is a strange presence in the house. We do not know what is real and what is illusion. I think there’s a scene where someone is in the shower, and girl discovers another self. I think the film was in English, so it is not Ju-On, although it has a similar atmosphere. If my memory serves me in the movie there was no blood, but it was very cramped and creepy. It looked like independent, small budget movie, maybe a TV movie.
It is possible that something of written I remember incorrectly.