We're gonna let you in on a little secret about Mama Jeanne. She, like her husband, is also based on a real person—Jeanne d'Alcy, who was a famous French film actress and star of many of her husband Georges Méliès's movies.
We don’t see much of Mama Jeanne, but we know that she used to be Papa Georges’ muse (and presumably still is). She’s extremely supportive and protective of her husband and helps him to hide from his past, probably because it hurts her to see him in pain.
She also has a whole lot of compassion. Even when she knows that both Hugo and Isabelle have stolen things, she helps them patch up their injuries and even gives Hugo a place to sleep. In other words, she's kindhearted, and definitely full of the motherly qualities that Hugo's looking for.