I've read The Passage - Justin Cronin. The series was great, but I haven't heard much about Jeanette (from what I can remember).
I really want to know if she's special like Amy.
My question is was Jeanette anything more than Amy's mother?
No. She was just Amy's mother, nothing special.
She had a habit of going out and coming back with men, having a one-night-stand with them. One night, a college frat boy tried to take her where she didn't want to go, and she killed him. After this, she dropped Amy at the convent, telling Lacey (who answered the door) that she was going to be right back.