When Jolie needed to find out. (spoilers)

At the start i apologize for my english.

So saw the movie a couple days ago and i really enyoyed it. Of course at the start i knew who the killer is. It was pretty obvious. Stil the movie was great and Etan Hawk acting was really good. Only thing that bugged me was when Angelinas characther found out who the killer is.

As all who have seen this movie - she finds it out at the elevator when he kills his mother. I think she should have found it out sooner. In the movies begining when Jolie`s characther is talking with him at the police station, he freaks out when he sees the stragling wire. Of course he was acting, but still. Then she says it`s a natural reaction for those who are normal people. Ok, understood.

Coming to the end of the movie, they fall in love or have feelings for each other, doesen`t matter. He comes to her apartment or hotel room and they start to have sex. At the begining it`s on the table, but then they move to the bed. As we see, Jolie`s characther has glued pictures of the victims on the ceiling, at one point Costa (Hawk`s charachter) looks at them and seems to be completly normal.

Well there`s my question - shouldn`t he be grossed out or freak out if he freaked out when he saw the strangling wire? Because those pictures were nasty, ugly and terryfying. She should have noticed it and arrested him at the moment, she should have knowed he`s the killer. Probably she was enyoying the sex and was cought in the moment but still, that was the moment when Costa gave his cover up.