Maybe. It depends on the theme and style of the existing stories in the collection. If the new short story fits well with the overall mood, for example, if it's a collection of horror stories and the new one is also a horror story with a similar tone, then there could be room. However, if it's too different, it might seem out of place.
It's a heartwarming Christmas story. It might be about the idea of making room in one's heart or home for an additional person or element during the Christmas season, perhaps a new guest or a new feeling of joy and kindness that the holiday brings.
I'm not sure specifically as I haven't read the exact story, but it could be a family, like a mother, father, and their children. Maybe there's also an unexpected guest who becomes an important part of the story.
Use vivid descriptions. For example, describe the lady's increasing panic as she hears strange sounds in the dark room. Her heart pounding, her breath coming in short gasps. Also, make the ghost's appearance really eerie, like it has a distorted face or glowing eyes.
One way is to review the existing horror stories and see if there are any that can be grouped together more tightly, thus freeing up space for the new one. Maybe some stories have similar themes or elements and can be combined in a sub - collection. Another option is to expand the overall storage or presentation space for the horror stories, like adding more pages to a book collection or more time to a podcast series dedicated to horror stories.