I watched this movie maybe 9-10 years ago, and I'm trying to find it for 3 or 4 years, and can't find it for the sake of my life. I also asked here 2 times last year and this user here commented that he knew the movie but couldn't remember it's name. And this is the closest I got, I tried every possible way I know, no luck so far. So anyway, the movie:
It's about a young girl with her father that moves in this town, starts to go in new school and soon befriends this goth-like girl that dismiss classes, drinks and smokes. Soon this goth-like girl (brunette) starts doing some bad things and kinda trying to ruin this other girl (blonde) life, like when she kills a guy in a hotel and wearing a blonde wig, so the police will suspect this other blonde girl. And then she killed some other girl. Then the girl and her father found that this goth girl was a psycho, and I don't know how the movie goes but I remember this psycho girl was in love with the others girl father and at the end all three were in some abandoned public swimming pool, where this psycho girl tries to kill this other girl and her father shot the psycho girl and that was the end I think. There is this part in the movie where they question if the goth girl exist at all because she disappears at a moment.
Another details of the movie is the goth girl hanging out at cemetery. Both girls were young probably 13-15 years, and I think it's TV movie. The movie was clearly American or maybe Canadian.