Long distance relationships!!

Long distance relationships are complicated and werid why do people have them do they purposely do it i think people have them because they wanna be with more than one person and everything i think that thats what they do and how they are it just hurts me to see that my sister is in this relationship and she cheats on her boyfriend cause she doesnt get to see him for months at a time and she everyday after school goes an kisses on this other dude every single day and it makes me mad cause this other dude is very violent and he knows that i dont like him at all and everything today which is October 8th 2009 i found out that he yells at her alot adn he doesnt let her hang out with her friends and he is racist cause her boyfriend is black and everything so she likes black guys which is normal alota people do i dont like him. The thing is is that my sister is cheating on her boyfriend with a guy that is dating her best friend and she hasnt told her best friend which makesme mad cause seh deserves to know cause her mom has brain cancer and everything so this is just gunna hurt her even more sooo yeah idk im frusterated with everything and i dont want my sister to do this anymore it makes me mad i cheated twice and i felt horrible but i told them and we talked about what happen and everything but idk i just can't belive somebody as good as her cheats on her boyfriend hwo i love wtih all my heart he is a great brother and boyfriend to her sometimes he can be a jackass but what guy isnt a jackass so yeah idk anymore idk why people are like that it just makes me mad that they are being like that and everything i just dont know what to do...