I took a year of ballet lessons just to spite my sister
Why did you go that far to spite her?
I thought she had a crush on the teacher and I wanted to prove a point to her.
While that's nice you learned a new skill for a whole year, your means of doing so is unjustified. There is no reason why you needed to spite your sister like this for so long, you are really nasty. It's not healthy to make your sister suffer constantly like that.
She started it first by bullying me. That wasn't fun.
Even so, you shouldn't have spent a year just trying to spite her. You should have just lived your life and dealt with it in another way.