I'm going to cause my mom to get into a wreck
Are you seriously trying to hurt your mom?
She always sides with my sister when my sister is completely in the wrong
While it can be annoying that your mom picks favorites, it's never worth wishing injury and death on her. That is just vile, and she is your mom so you need to think more highly of her. She has her reasons and you must respect things even if you don't like it.
I know why my sister always gets away with her shit and that is because she is just like my dad and my mom doesn't stand up to them. It's just not fair.
Your family sounds like a mess, but hurting them is going to make everything worse. You can't fix how others treat you, but you can show them how you want to be treated. Be the better person and show them kindness, they might return it later.