To be honest, I think the point she's making is... well, not to put too fine a point on it... absurd! Or perhaps just deliberately provocative. A book should be as long as it needs to be. A 20 page short story can be too long, and a four-volume tome can be too short. I don't hear anyone saying that a Beethoven symphony should be cut by a movement, or that a Britney Spears song needs another three verses!
I often find that I will get through a long book more quickly than a short one, if it's better quality. A Suitable Boy, for instance... I just steamed through that in a few days, and there's no fat in it - at 1500 pages it's not a page too long. On the other hand, I've had 150-page paperbacks sit on my bedside table for months, just because they never captured my imagination.
I know that I always look forward to discovering a really long book: the anticipation of losing myself in a fictional world, getting to know the characters and share their lives... The longer it is, the sharper the sense of loss when it ends. The pleasure I get from a really good, LONG book is far greater than I get from even a superbly written novella.
One of the beauties of e-books is that I no longer notice how long they are. So I find myself reading a wider variety of books than perhaps I have in the past. You judge an e-book by its quality, not its length...