Heather is an important character on Chicago Fire since she’s the widow of Andy Darden. Before his passing, he was a firefighter on Truck 81 assigned to Firehouse 51. He sadly ended up getting killed in the line of duty, leaving Heather to blame his death on Kelly Severide. She feels that if Kelly hadn’t convinced Andy to pursue a career as a firefighter, her husband would still be alive and well today. Before Andy’s death, they were raising their two sons, Ben and Griffin, together.

Source: https://www.distractify.com/p/who-is-heather-on-chicago-fire