I would like to point out that the Changelings, or at least the other Changelings showed a great ability to impersonate solids.
If they can do that and sometimes/most-times they are so good at it that even friends don't see a difference, I would expect that she would have a better grasp on reality.
Or could the reason be the sickness
Also possible is -although not much, that there are different sorts of Changelings: infiltrators, scouts, rulers, "royals"...
If she is of the last type, then of course she doesn't know how the world runs...