As has been well documented here on FR (remember the extensive and entertaining research by 'Dukeman'?), Hillary definitely had a reason to believe things would change, but not for any publicly explained reasons provided by the willfully/blissfully ignorant media on this point.
No, the reason Hillary didn't expect it was because she had her own personal staff attached to the Oval Office whose primary job it was to spy, screen, and police such activities.
That's why Nancy Hernrich (sp?) and others whose names I've forgotten were posted in the jobs they held (they reported directly to Hillary, as did Sidney B), and that's why Lewinsky was kicked out early on from the WH and banished to the Pentagon (understand that to outright fire her would have unwisely tempted her to go public) early on in their affair, well before anyone like Drudge had an inkling as to what was going on. THAT'S when Hillary found out about Monica -- perhaps a year earlier then provided under the 'cover-up' story line.
I'd like to see one reporter find the right people who can verify that Hillary ordered Lewinsky's exile -- that would prove the lie once and for all.
Hillary's rage must have been based on the fact that Bill's people outwitted Hillary's people and permitted Lewinsky to covertly return, i.e., Betty Curry. I'm sure Betty could tell quite a story -- and why, pray tell, isn't the press offering $1M for HER story!! (Hint --they are not really interested in the truth). And there's even a reasonable chance that she might even tell the truth!!! And remember that when Lewinsky was banished to the Pentagon, the Hillary spies (who had obviously failed in their job) were fired -- and who do you think fired them? (Hint -- who hired Craig Livingston?)
Instead, the press reads the story, with its conflicting tales i.e., Blumenthal, as if it were a mystery novel wherein one story line is the truth, the others false leads. That's an entirely false reading -- because in the Clinton White House, ALL the story lines are false, and the contradictions between them are merely artifacts of the basic problem of coordinating lies -- that it's not easy to do, after all.