Reaction to Gregor as Beetle

I still find it odd that the initial reaction to Gregor's transformation was not one of incredulity, but of acceptance. At the end of Metamorphosis Greta finally says that perhaps Gregor is not a beetle, but maybe the beetle is just a beetle. While Kafka may be referring to some type of "sixth sense", or pure rationality (how could a three foot beetle be in Gregor's room unless Gregor turned into a beetle, or a beetle ate Gregor?) I find it more likely that Kafka has crafted a scenario where there is no solid reading. Or perhaps my oxycodon is making me write nonsense.