I just reported my friend.
What was the reason why you reported your friend?
Because he hurt my sister, and I can't stand his behavior any longer.
Caring about your sister is important, but you should also keep in mind that it's important not to betray your friend. Reporting your friend may have been an overreaction if it was only for a minor argument. If it was something serious though, you should report your friend.
Why wouldn't I overreact? He hurt my sister and needed to be punished.
Well it really depends on how your friend hurt your sister. If they simply broke up from a relationship than it may not be realistic to be upset with him for that. If he physically hurt your sister however then it makes sense, and if you have to betray them for something like this then so be it.