A friend of mine was recently caught in the middle of drama. We'll call this friend Jim. Sally told Billy a lie about Jim. As a result, Billy is now mad at and not really speaking to Jim. For the moment, this lie has wrecked that relationship.
Jim and I talked about it for a while and he finally asked, "Is it okay that I'm mad? Is it wrong for me to be angry about this?"
The answer? It is perfectly normal for you to be mad, disappointed, hurt, and angry when somebody wrongs you. It is not a sin.