Hide question

The book is not hide! It just wouldn’t let me post without a book name. I am trying to find a book that I read about 12 years ago. I barely remember much but I remember there being a girl in a mental hospital. I vaguely remember that maybe she didn’t belong there and was trying to scape? I sort remember a part where she may have been in the air conditioning vents? Also, I remember later in the book, maybe the end, the hospital catches fire? And she finally gets out. I don’t know. I know that isn’t much to go on but I thought it was a book from Lisa Gardner but I don’t think it is anymore. The only book I found of hers with a mental hospital was Hide but that was about an abandoned mental hospital so I don’t think that’s the right book. I’m literally desperate to find it lol