Twilight was not born with wings, thus she is not used to having to handle bird instincts, thus has not built up the self-control to resist nesting instincts, nor does she even recognize that she’s nesting - she thinks she’s just getting herself cozy XP
True x3
Well why do you think she chose books for her nesting material? Xp
Nah, it’s just bookhorse in her natural habitat, methinks x3