I've been reading up on vitamin E in cats, and it turns out that in sufficient quantity it's something of an appetite suppressant. Try puncturing a vitamin E capsule and letting her lick it off your fingers (apparently it tastes really good - not to me, but my cat assures me it's delicious). See if she's still such a vacuum cleaner after a few days of that. At least according to this website, cats haven't been shown to be capable of overdosing on vitamin E.

Love, Columbine (who has a hard time rubbing it on Smudge's ouchies because he wants to lick it all immediately, and he's now refusing even his beloved CET Chews...)