I assume the 5 year old snuck out. You do your best as a parent to keep your kids safe, but if a 5 year old has never unlocked a door and gone out at night, it is easy to believe it would never happen. Then the little child thinks Fido is in trouble, and of course in her innocence and lack of wisdom, she is going to check on Fido.
I really don’t think this is the Moms fault and I really don’t think Mom was aware of her child being outside until the screaming began. If anything, it is good she heard the screaming. If she was a heavy sleeper, the girl would have been eaten by now.
And mom has to sleep some time!