A film with a david lynch/guillermo del toro feel to it. Possibly in Spanish, though there's barely any talking in it.
About a girl who is having a "coming of age" party with her family. She's reluctant to go, keeps hallucinating about a horse and a young girl in a forest. A plant starts growing out of her mouth and choking her.
I really remember the scene where all the guests start tearing meat of a horse's head at dinner.
At the end of the film she dies trying to pull the plant out of her mouth.