I...honestly don't even remember x3
I'm not really one to keep track of individual lines from shows and such, as there are hundreds per episode practically.
Buuuut just to answer...when Twilight freaks out in Forgotten Friendship over not finding anything about Sunset being forgotten by everyone, so she's all like
"I'VE ALWAYS BEEN GOOD TO YOU LIBRARY!"
inb4 a bunch of people say “Yeah, yeah, we get it- LIGHT ‘ER UP, LADIES!”