Sister says I tried to hit her

I (18) was in the kitchen with both my older brother and sister, i was talking to my sister (30) and she suddenly screamed for no reason and then ran to my mom saying that I had tried to hit her, my brother just started laughing and looked at me because we both knew that it wasn't true. My parents don't take me seriously, I keep trying to tell them what happened and that my sister is mean to me and that it hurts that she accuses me of trying to hit her, my mom just closes the door ignoring me :C I tried to tell them again and she said again that I tried to hit her and that I scare her.

They always support my sister no matter what she does, and hate me and yell at me for no reason...