Did I do something wrong?

I told my mom about my day and also about a journalism project that was presented in our class this morning. Anyone who wanted to could sign up for it. I'd definitely like to be an author (everyone around me knows this), but I didn't sign up because I don't want to pursue a journalistic writing path. I'd rather write whole books.

My mother, annoyed, said she didn't understand why I hadn't signed up and said I would never get involved in school-related activities anyway (like choir, or general clubs, etc.). I replied that I simply didn't want to, since I also have training three times a week and a lot of work to do for school. I also explained that I simply didn't want to pursue a career in journalism.

She then said that she didn't understand why I was telling her and what I wanted to study later… you can't study book writing, journalism is the closest thing to that.

I said that I don't even know what I want to study (I'm only in 8th grade) and that I told them because I just wanted to talk about my day.

Then she said angrily that it would have been a good opportunity for me and that I could get involved in school, and then she left my room.

Now I'm wondering if I did something wrong, and I'm also a little sad that my mother can't accept my decision. By the way, I'm in a club, but I just don't feel like doing anything more. What do you think?