Door lock

Your sister definitely sounds like she needs professional help, and I'm sorry to say, but your parents could use some therapy as well.

You need to be away from her. Do you have relatives you can live with? She sounds as if she is out of control, and it seems your parents are unable or unwilling to protect you from her.

Did you ask why she did that?

I'm sorry ... that is terrible.

@Broken That's stupid. It seems like she's really jealous of you being with him. That's still not a valid excuse though.

@Broken That's simply rubbish, she was talking as if she cared about you and yet she used a baseball bat to hit your legs.

Sounds like she's a psychopath.

Your sister is an emotionally challenged lunatic.
Call the cops once and see how quickly she calms down.
If your parents let her behavior slide, their behavior is questionable too.

Hit her back