The irony here is that the "absentminded professor" stereotype is fairly well known, so "disorganized" and "professor" aren't necessarily contradictory terms in that sense, so it's almost par for the course instead of an exception that she's a disorganized professor, but she probably forgot that, being the embodiment of the aforementioned absentmindedness.

Anyway, she probably meant "a paradox" or even " ironic," since an oxymoron is a rhetorical phrase which contradicts itself, which the term "professor" doesn't do on its own. Paradoxically, or maybe ironically, I think, she absentmindedly uses "oxymoron" instead of "paradox" in a statement about a supposed paradox which isn't a paradox at all, since nobody considers "disorganized professor" to be an oxymoronic phrase.

That's some kind of conundrum, or something. Sorry if my thoughts on this subject aren't more organized.