Who is Mama, Paw from The River Between Us and what is their importance?

Mama is Tilly, Noah and Cass' mother. She was more or less a single parent, as Paw disappeared several years before. At first glance, Mama appears to be tough and stern, but she also has a deep relationship with Noah, of whom she is extremely protective. Mama is also close to Cass, due in part to their both having the capacity for visions.