Everywhere I Look, I See A Book...

I am 12 years old, but despite my age I believe I am a good writer. I took a creative writing class for 5 weeks and have improved. I have a really good idea for a psychological horror novel, and I have this habit of pacing around outside for hours directing a movie in my head. I have mapped out every scene, every detail, the only problem is I can't find the time to write it down. And I'm always being inspired by random things that form intricate plotlines, and I can't help but pace around and create those too. It's very upsetting when I tell my mother this is what I want to do in the near future, and she just looks at me like I am a five year old saying he wants too be an astronaut. She thinks that the book is a kids or young adult book (which it isn't) sorry, but that's just not my demographic. She doesn't believe me, or understand me even though she is an english teacher. Most of my teachers really like my writing and I think it's kind of a duty to write. I have to, it's like an impulse. I am also artistic and plan to make a movie or short with 2d- animation. I started drawing some scenes with a manikin, and I will do the less important key frames with a graphics tablet. I also really want to write something focusing on a zombie apocalypse that spreads as an std, and a historical fiction novel on the French Revolution.