Friendship- my definition- is built on two things. Respect and trust. Both elements have to be there. And it has to be mutual. You can have respect for someone, but if you don't have trust, the friendship will crumble.
She was afraid that it was a moral issue, and that was one of his weaknesses. He was Salanders friend. She knew her brother. She knew that he was loyal to the point of foolhardiness once he had made someone a friend, even if the friend was impossible and obviously flawed. She also the friend was impossible and obviously flawed. She also knew that he could accept any number of idiocies from his friends, but that there was a boundary and it could not be infringed. Where exactly this boundary was seemed to vary from one person to another, but she knew he had broken completely with people who had previously been close friends because they had done something that he regarded as beyond the pale. And he was inflexible. The break was for ever.