I have some sympathy for Oprah's staff here. They have a deadline to meet. If the guest doesn't show up, they can't just shrug, and tell the audience, "Sorry, we don't have anyone to interview today. You should all go home now." If the guest has vanished, they need to create a whole new show on the fly, with new guests, new script, new technical details, and they need to do it in an impossibly short time. Not to mention legal issues - did advertisers pay more for a slot for a guest they thought would bring in a particular demographic?
The guest not being there *is* a catastrophe to the staff. While Oprah may make it "all about her", I'd say that risking missing a commitment that is as critical to a large group of people as doing a tv show, is rude and unprofessional.