Obviously, ALice is nuts. She's concocted this entire story--which is obvious when the other girl reads the script at the end. It's a word for word play of what has 'happened' to Alice--all in her head. Then, at the very end, with parts lost somewhere in another plothole, you see that Alice has been obsessing over the ambiguous lesbian friend--filming her while she sleeps and saying creepy things.
The director wants you to THINK it's a supernatural thriller, that there are ghosts, etc, but it's just a movie about a schizoid chick. It's completely botched by the lack of a good writer/s. This could have been pulled off, ala Secret Window, but...as I said, BAD WRITING. It's not the ending that's slapped on or badly written, it's the bulk of the story that isn't fleshed out. They focused on cinematography and atmosphere, rather than in storytelling.
Could have been a good movie. Even for a Murphy flick! (dear Lord, we haven't forgotten the abomination that is "Ramen Girl", have we?)