My Grandmother used to hit me when I was a child, what can I do now?

When I was about 6-8 my grandmother moved in with my parents and my younger brother. My parents were having problems and she used to watch my brother and I. While I was younger though I have distinct memories about her hitting me and pulling my hair as a punishment. The worst incident I can think of is when I dropped a bowl of cereal and she hit me with a broom. I'm now 16 and my grandmother has moved in again, she constantly hares me and goes through my things. I confronted my mom about how she used to hit me when I was younger and my mother told me how her own grandmother did the same. I want to take legal action but don't know where to go, and if someone has any advice I'd gladly take some.