Hannah Gruen is the live-in cook-and-housekeeper of the Drew family. After Nancy's mother passed away, Hannah took it upon herself to act as a motherly figure for Nancy and helped Nancy's father, Carson, to raise her. Since Hannah's never mentioned to have had any children of her own and has been working for the Drew-family for such a long time, Hannah seems to see Carson and Nancy more as a surrogate family than her employers. She is a natural in the kitchen and always manages to impress and please Carson, Nancy and their friends with whatever delectable dish she has whipped up. She often worries about Nancy's well-being when she is out solving a case and she offers her wise advice that Nancy takes into consideration and greatly appreciates.

Hannah is a very clever and brave woman in her own right. She has made homeade burglar systems and has courageously stood up to intruders and miscreants when Mr. Drew isn't present. Overall, Hannah is a sweet woman who has proven to be invaluable to Nancy and her father.