ABANDONED. YA book about a girl and a boy in the attic. Turns out they are “actors” in a simulated environment

[Mico]

Need help remembering the title of a book. I think I read it before/during hunger games era

Here's what I remember:

Girl is living in the modern timeline. In the attic of her home, she has glimpses of Boy who is from a much older time. Like 60s or earlier. She thinks he's a ghost, a former occupant of the house. Things happen and it turns out they are both 'actors' in a simulated environment. Think The Truman Show but on a wider scale. I think they try to escape at some point.

[Kris]

Does anything in the Reality Show Themed Novels sound familiar?

Around what year did you read this book? A range of years is fine.

How far into the story do you learn it's a simulated environment?

[Rainbowheart]

Still looking, Mico?

[Kris]

No response, moving to Abandoned folder.

Mico (OP) was last active on the site in November 2020.