@Spearmint
I don’t think there’s any reason for any of them to be those things, but wasn’t Dashie quite fond of Zap-Apple jam? (This situation might’ve killed her love for that though.)
@redweasel
Because she’s the only “mane” character left, (besides Spike, but he’s probably a Pitaya for all we know) and because Applejack is the most loyalest, and dependable of ponies.
Welp that one person who was trying to make “Twilight is an eggplant” a thing, was successful in his attempts after all. Also Dash reminds me of a zappapple now :p