"Princess Celestia, it’s Princess Twilight. You need to come now. It’s horrible."
The first spell didn’t work. Neither did the second. The third spell opened a gash in Celestia’s foreleg, pouring blood back into the body. An old fashioned skin knitting spell, then the shock. Shock! SHOCK!
The purple alicorn’s hoof gave a twitch, and then, thank the Heavens, she moaned!
"Ssssles’tia?" The voice of Twilight slurred out, as if waking from a deep sleep.
Tears fell from the monarch’s eyes as she held her beloved former pupil close. “Twilight! I was so worried I might have lost you.”
Twilight couldn’t find the words in time, so she settled for hugging Celestia close, and stroking her neck.
"Oh, my dearest Twilight, even with your injuries… You truly are the best of us."
So she lived, truly, deeply and well. Her disabled status had little impact on the fact, and her adventures afterwards bore proof of that.
-Twilight diving into a pool, and forgetting to remove her regalia.
-Twilight comes into a meeting late, having forgotten a tool with which she could write, and says, “I need a utensil.” When everyone laughs, Twilight’s in that number.
-Twilight's friends slowly learning to accept her as she is, and giving her love that is unpatronizing.
-Twilight being held by Celestia as she cries, bewailing her lost focus… Only to be reminded that it has made her ability to come up with new ideas all the easier.
-Twilight being able to fight all the easier, because her thinking style is uniquely geared to notice new things, and respond to them as quickly as possible. She continues to be a heroine.
-When Blueblood spouts disability related slurs at her after his trial, she gets the unique pleasure of seeing his many times great grandmother zip his lips closed.
The new Twilight is disabled, no bones about it, but when you’re a ruler, societal disadvantages have a way of removing themselves. She has a very happy life, despite the fact that her mother considers her injuries to be a waste of a great brain. Her cognizance only makes her feel the pain of rejection all the more, but her cognizance also tells her that she has a mentor who loves her, and knows her brain isn't wasted.