Melinda was long past judging anyone based on superficial traits such as Bloodline or how much they smile or even how kind the smile appears.
Life was never just Black and white sometimes. Her uncle used to smile at her a lot, he was always a kind Elder but that did not come into play once she crushed his Son's family jewels.
Her way of thinking was much clearer now. She was not after a goody-two-shoes with a strong sense of justice, she was after someone she could feel that connection with.
Hal just happens to be that person.
The fact that he is a Devil (which she was not truly buying though. After all, the information had come from an intruder with a terrible way of earning trust) did not change a lot. She was a little upset he was not upfront about it though. But then again, she had kept her Bloodline details secret from him as well.