Since in the immediately next part the protagonist assigns a 50% chance on a monster being behind her back (because she doesn't know for sure either way), I'm guessing that the concept of having reasonable priors is one which is supposed to get gradually introduced. This early on, the character's estimates seem to be tending to go from a false 50% to either a false 0/% or a false 100%.

So, yeah, what you suggest is probably too complex to start with.