Another factor is the backstory. If there are rumors or a known history about the mama that involves dark magic, death, or some kind of curse, it adds to her scariness. Maybe she was once a kind mother but then something tragic happened that changed her into a malevolent being. This transformation and the mystery behind it can send shivers down the reader's spine. For example, if she was cursed by an evil witch because she didn't pay a debt, and now she's out for revenge on the world around her.
One mama scary story is about a mother who lived in an old, creaky house. Every night, her child would hear strange noises coming from the attic. One night, the mother went up to the attic to investigate. When she opened the door, a cold wind blew out, and she saw a pair of glowing eyes in the darkness. She quickly shut the door and ran back downstairs, but the noises continued throughout the night.
It's hard to say for sure. 'Mama' could be inspired by real-life incidents but have a lot of fictional elements added for entertainment value. Or it could be completely made up from the imagination of the creators.
I'm not sure. It's possible that 'Mama' has elements of truth or it could be a complete work of imagination. Without more context, it's difficult to tell.