Well, the background I'm thinking is Crystal Empire, it's not like she can get to read the Empire's library books very often, right? And she can't help it but to read at night, but caught red handed when Cadance was getting some water and she notice there's light in her library.
"... Read me a bedtime stowy? :3" "Twilight, you're too old for that kind of stuff now. " (walks in, wearing a nightcap) "Nonsense, bedtime stories are just as appropriate for the young at heart as they are for the young of age." "Dear, it's past midnight already. Don't be encouraging her." "Sorry. " "Pwetty pwease with a cherry on top, best sister-in-law? " "Oh alright, I'll read you a story." (Fluttershy-style "Yay!" followed by Pinkie Pie-style bouncing around in excitement)