It may be more accurate to say that when she sees a red object, that generates a feeling of surprise, because her visual cortex is doing something it has never done before. Not that there was ever any information missing -- but the surprise still happens as a fact about the brain.

We measure information in terms of surprise, so you're kind of contradicting yourself there.

The entire "thought experiment" hinges on getting you to accept a false premise: that "knowledge" is of a single kind. It then encourages you to follow this premise through to the seeming contradiction that Mary shouldn't be able to be surprised. It ignores the critical role of knowledge representation, and is thus a paradox of the form, "If the barber shaves everyone who doesn't shave themselves, does the barber shave him/herself?" The paradox comes from mixing two levels of knowledge, and pretending they're the same, in precisely the same way that Mary's Room does.