Im surprised nobody has commented on this beautiful chapter. Honestly everyone's motivations feel so real, its very easy for me to imagine someone actually shutting himself out and denying the truth just because they didnt want to admit they were involuntarily involved in a murder, or that there was a way they could have prevented it, no matter how unreasonable.
Also, the detective's assumed past also explains his acceptance. He's already experienced and felt that (if its true) so it makes sense he would be used to her.