Swimming Pool

Has anybody seen this movie? I read something about it last year but never got the chance to see it, the only thing I remembered was that the protagonist was naked half the movie.

Then last night, I was going through all the channels before going to sleep and I saw this naked beauty walking around a pool and then she started swimming. The rating said Rated R so it wasn't porn, and that's when I remembered that I knew this movie, it was Swimming Pool (Written & Directed by François Ozon), and even though she got on a bikini, I kept watching.

The movie is really good and simple, and Ludivine Sagnier's Julie is a beautiful young french girl and her acting is great. I didn't like Charlotte Rampling's Sarah much (though she's naked too in the movie) but that it's possible cause Julie was adorable.

So the movie was great, I liked it a lot, BUT, I didn't get the ending I think. It was kind of confusing. I mean, I have a few ideas of what it was but none sound completely clear to me.
I'm going to ask some people that have seen it already and then I'll be back with an update. Or better, if you've seen it, post a comment and explain it to me :)


UPDATE @ 3:40pm: after talking to some people, I thought about some explanations for the ending, though no one knows for sure which one is it.

I thought that the writer made the hot girl's story up for her book. But I dont understand why, cause she was writing a story and everything before the hot girl came to the house, and she even continued writing a few days with the hot girl living there. She seemed to have changed stories and started writing about the hot girl when she saw her having sex with everybody.

So my question is, if she was in fact alone and imagined the story, what made her change the story of her book? cause she sure wasn't writing about the hot girl from the begginning.
And, if it was all her imagination, why would she go against her publisher? (who was supossedly the father of the hot girl) and why would her leave a signed copy of the book for her?

Now, my other idea came from the final scenes of the writer waving to the little girl (who looked like a 12 or 13 years old) from the balcony. Cause then I thought that maybe what happened was that THAT little girl came to the house, and she used her as a character for the book, and imagined everything else. But if you think about it and you see the little girl, she looked too young to go and live by herself in a big house in the middle of nowhere in France.

Again, pretty confusing.