Justin beiber over a friend?

okay so, im 13 years old & just a few days ago i was talking to my sister's friends jewl and hanna i told them ''do you guys still like jb?'' they both said ''yes'' (they are 9) then my sister who is 10 said '' i dont like jb'' jewl punched her as hard as she could (my dad and jewl's dad were talking from afar, but i guess they did not hear anything going on) then my sister said '' JEWL!.....well freak ( not my real name but im going to use it) doesn't like him to!'' then jewl looked at me like she was tough ( im WAY taller than her) i ran because i didn't want any crap started i couldnt run becuase my legs were weak (my body is not in good shape..) so i stopped folded my arms and just let her hit me the she punched me 2 times hard as she could in the worst place she could ever hit me..my back i have problems with it...i tryed not to cry i almost fell to my knees, then she sat down and said who doesnt like him? i smiled weakly and said ''everyone loves him'' then i told my dad he said ''well im sorry you dont tell her dad she hits you and lila (my sister)'' i fell into tears because the pain and what he said but i know he is right...but im to shy and nervous to say anything, i dont talk to no one & when im depressed or angry i just go to my room and lock the door...but when im not there with my sister i know jewl probably beats her..i took the hit for my sister many of times when lila does what jewl doesnt she pinches & punches her, one time i protected her because jewl picked up my broom and was hitting me with it because i wouldnt let go of lila....should i tell her dad or mom what she does? they scare me though...and if i should what do i say? im thinking of commiting suicide because of almost everything....ive already tried....i have nothing against jb he makes good music its just not for me though :/.....im alone in this world anyway..i need help on this...i know im an idiot