I've been thinking about this for a bit now and thought I might share it. Let me know what you guys think in the comment section.

Queen Isabella visited the pavilion at age 16, when she discovered the gateway in her room. After the third night, the land vanished 'forever'.

The magic she got to keep involved two things. First, she was able to find a way for her daughters to see the realm one day. 

And second, Isabella was clairvoyant.

I know, I know, but just hear me out. 

She knew she would one day have twelve daughters, so she wrote the story and made 12 copies, each with a different flower on the cover. Her room became her daughters' room when Ashlyn was born, and she had the garden built to look like the pavilion, with a secret way out since she knew it would be needed one day.