Definitely not. 'The Landlady' is typically a made-up tale. It might draw inspiration from various sources, but it's not a true account of actual events.
Yes. My Demon originated from a manhwa and has made certain changes to fit the medium of the adaptation. But the core elements and storylines are drawn from the manhwa source.
The full story of 'The Landlady' is a tale of mystery and unease. A young man, in search of accommodation, stumbles upon this boarding house. The landlady seems warm and inviting. But then, the details start to add up in a menacing way. Her fixation on the young man, her strange behavior around her stuffed pets, and the way she seems to be hiding something all point to a disturbing truth. It seems likely that she has been preying on the young men who have come to stay at her place, perhaps drugging them and keeping them there in some way, though it's not fully explicit. It's a story that builds tension and leaves the reader with a sense of dread.
In 'The Landlady', one of the key aspects is the sense of unease. The landlady seems overly friendly at first, which immediately sets an off - putting tone. Dahl is masterful at creating this kind of subtly creepy atmosphere.
To be honest, I don't know. It depends on the author's inspiration and the background of the creation. Sometimes, even if it's not a completely true story, it might draw elements from reality.