Knowing Twi, she probably already read it, as well as a few guides to flight long before this is going to happen (dumb timey-wimeyness of spoilers). It wouldn't apply to her, but on the other hoof... UNREAD BOOKS!!
is this even true? can you show me 100% indisputable proof that twilight sparkle will ascend to Alicorn? or is this just another fan bias? there was rumor that derpy would be removed from the show. and she wasn't. or how there would only be 2 seasons and hasbro had cut all financial support of the series. or any other false rumors surrounding the canon. people are treating this as if its true and already happened. but this hasn't happened yet. maybe its true maybe its not. always assume rumors are false instead of true. say this is true. i see some pretty cool lessons to be taught regarding it.
the authentication (despite being on hubs page) has been disputed. considering how this image does not follow the design interface used previously by the hub (not the animation. the logo's and what not) also that this image is so far the only thing hub has said regarding the subject. don't you think there would more official content on the matter? and finally, concept images such as sketching and digital cells from season 4 have been released to the public. in none of these images has twilight been seen as an alicorn. perhaps these were scraped to make way for this change that may have come at the last minute. or maybe these were images of her before ascension. all i am saying is despite being on the hubs facebook, this is still lacking backbone. companies have screwed with their fans before. in this same way. if she does become an alicorn, this will be an interesting and overall welcome change to a franchise that is becoming somewhat repetitive between events, season premiers, and finales