In Chapter 7, Twilight's imagined worst-case scenario of what will happen when she comes out to her friends: Rarity spreading the news and ruining her reputation; Rainbow Dash's work and speed training suffering; Fluttershy becoming negligent with her animals, letting them spread diseases; Applejack banning her from Sweet Apple Acres; Cheerilee banning her from the school, and her students avoiding the library, resulting in literacy rates and pony intelligence dropping; and Pinkie Pie being thrown into depression or worse when nopony turns up to the "New Marefriends" party she'd inevitably throw her and Derpy.
Complete social upheaval, dismal weather for eternity, sickness running rampant, driving students from the ability to learn, and the friendliest pony in town thrown into insanity, and it would be ALL HER FAULT.
In Chapter 9, Twilight brings up the likely possibility that Pinkie Pie will want to throw a "New Marefriends" party for her and Derpy. Derpy asks her to make sure she doesn't make muffins, as she hasn't been able to look at one since the Baked Bads incident (ie, the whole reason Derpy is associated with muffins by the fandom to begin with).
When Derpy arrives at the library in Chapter 19, she calls out to Twilight, who rushes to her with no regard for what's in front of her. By the time she skids to a stop, her mane is askew, her hoof is caught in a stepstool and she has a book skewered on her horn. It takes a while for Derpy to stop giggling.