Who is Anne-Marie Marrone from The Pact and what is their importance?

Anne-Marie Marrone is the first police officer on the case after Emily dies. Sadly, it is Marrone who makes the big mistake of not doing a gunpowder residue test on Emily's hands before the hospital washes her. She also believes that Chris is guilty because of the pregnancy. Marrone later changes her opinion when she sees Chris' reaction to the news of the pregnancy.