I was listening to some Japanese children's songs.. specifically "Toryanse"..
7 used to be an important age in Japan, as children would often die before then. At the time of the child's birth they would take a talisman from the shrine, which would be returned when the child is 7. In this song the parent with a child (7 years old) is talking to a guard about passage to the shrine, the guard replies that going in is easy, but returning is scary (as you'll be without the talisman of course).
This reminded me of Silent Hill, and of course Cheryl's age. I didn't know she was 7, but after reading this text I immediately thought it would make sense if she were 7 (and she was
). Also the Flauros in the beta version is called the same Japanese word - talisman. So it sort of makes some sense in regards to the game's story.. though not a perfect explanation of anything obviously.