] While she certainly isn't in hysterics, like Marianne, Elinor's good sense, (as we have seen it), should have prepared her for the event better. The veneer of her sensibility has been cracked...

...that for all her 'sense' and ability to keep everything under regulation, Elinor does have some very romantic thoughts and notions and hopes of her own. To me, this comment is similar to Elinor's earlier wish to believe that the lock of hair Edward had in his ring was her own procured by some type of (very uncharacteristic) subterfuge!

Both are reminders that she is, when all is said and done, also a teenage girl in love.

Another interesting idea there is in "the difference between the expectation of an unpleasant event, however certain the mind may be told to consider it, and certainty itself."

More than one character has had to live through this very circumstance and learn this difference.

--Colonel Brandon had the expectation of hearing that Marianne was really engaged to Willoughby and then met with the (supposed) confirmation of it (even though it was not true, he still went through believing that it was 'official').