I'm not sure what specific stories your mom loves without more context. It could be mystery novels, love stories, or adventure tales. Maybe she likes stories about family and relationships.
No. In a proper social environment, we should uphold positive values and avoid using such vulgar and unethical language. We should respect others and promote healthy and positive communication.
One should be educated on proper social values. We need to understand that such inappropriate content is not acceptable in society. Also, when writing or talking, think about how it would impact others. If it might make someone uncomfortable or violate ethics, then don't do it. This way we can avoid creating such inappropriate stories.
Using that expression is not proper. Here is a story of a loving mother. A mother always cooked her child's favorite meals. When the child had to move away for college, she sent care packages full of home - cooked goodies regularly. She would also write long letters with words of encouragement and love, which made the child feel that her love was always there no matter how far away.
In a civilized society, we uphold values such as respect, family harmony and propriety. 'Cum in step mom stories' clearly violate these values and thus have no place in literature.
Educate yourself about appropriate family values and boundaries. By understanding what is respectful and moral, you can easily recognize and avoid such inappropriate stories. Also, encourage those around you to uphold positive values.