The week before Christmas was filled with excitement for 6-year-old Macenzie and her mother, Lacie Simmons.They decorated the tree, shopped and put an inflatable snow globe in the yard. The festive mood ended abruptly Dec. 20 when Simmons collapsed in the hallway of her parents' Grand Prairie home. When the EMTs arrived, Macenzie clung to her mother."I just need to take care of my mom," she repeated as she patted her mother's arm. It was the last time she saw her mother alive."Her blood pressure bottomed out, her heart failed and that was it," said Lacie's mother, Renee Simmons.Within 26...