Is it right that my little sister gets to hit me but i dont get to hit her back?

this has been going on for years. she's 8 and im 14. both girls. so anyways, she's always hitting me. if she gets mad she hits me with all her might. i admit it doesnt hurt as much, but isn't it still wrong to do it. even if i slightly hit her she starts crying to my mom or dad. even if i try to reason with them i'm still wrong because i'm the oldest. if she grows up thinking its alright to hit people when shes mad chances are somebody's going to hit her back, hard. it gets so annoying. what should i do? she's driving me nuts.