Is it ever ok to slap your younger sister if she misbehaved or do anything severe?

i am 28 years old and my sister is 13 yrs younger then me (15).we've lost our parents in a car accident,i ws 17 nd c ws jst 5. thereafter we grownup undr the care of my grndma who passed away jst 3yrs ago.nw i am practicing in calcutta HC as a civil lawyer. c is in her 9th stndrd. i'm her legal guardian. lst n8 i caught her while c ws havin a horny chat wid an unknown guy(thankfully c don't hav an web cam). it shocked me bcoz c is only 15 nd her board xam is knockin d door!! i gt vry angry nd cudn't cntrl my anger nd gave her so many tight slaps(which ws very hard bcoz my hands were also aching ) nd c fell down nd her forehead ws hrt by d wooden corner of d bed nd it ws bleeding.i ws so upset so i scolded her a lot nd punished her by disconnecting net connection 4m her pc nd takin her mobile. c ws cryin den silently, bt aftr c undrstd her fault nd came nd hugged me tight nd said sorry, c ws cryin dat tym. my gf ( c is my backbone since i lost grndma) told me dat i sudn't slap her as bcoz c's too young. but i'm vry much caring nd strict abt her including her studies. i used 2 punish her by ear pulling or ussually i scold bcoz of her studies.bt ystrdy i slapped her nd d cheekbones gt red. i'm feelin so sad 2 c dat. i took her on my lap when c ws born, i still remember c ws lukin lyk a little snowball den.i really love her nd care 4 her. bt i can't cntrl my angr wen i sw her doing dis typ of things though c said dat c hs done dat horny chatting only 3 times nd promised me c'll nevr do dat again. i jst wnt 2 ask u is it ok 2 slap her? bcoz i'm really distrbd 4m lst n8 regarding dis issue!