Hard to say. There might be elements of truth in it, or it could be a complete work of imagination. You'd need to look into the background and the creator's intentions to know for sure.
I'm not entirely sure specifically what 'lillian121 fanfiction' is about without more context. It could be fanfiction related to a character named Lillian, perhaps from a particular book, movie, or TV show.
The Great Lillian Hall is purely fictional. It was crafted by the author's imagination and doesn't draw from any true incidents or actual individuals. The story is designed to entertain and engage the readers through creative storytelling.
Since I'm not familiar with 'lillian121 fanfiction', you might want to join relevant fan communities. There, you can ask fellow fans if they know of any good 'lillian121 fanfiction'. They may be able to point you in the right direction based on their own reading experiences.
Mrs Harris is typically not a true story. It might incorporate fictional elements, settings, and events to create an engaging narrative for the audience.