Boy gets drowned in pool, Mom seeks revenge

I cannot, for the life of me, find the title for this.

This was a movie that I saw on IFC sometime in the early 00s. It was not a movie made in the United States, but I can’t place the accents. The biggest plot point that I can remember is a teenage boy being held underwater by a girl and her boyfriend in a public pool, I believe resulting in his death.

The boy’s mom then sets out to take revenge on the unrepentant girl. I vaguely remember the girl setting the boy up so they can get him to the pool with her. The girl was an absolute sociopath, extremely unlikable.

Any ideas?