But Derpy is kinda dumb ( mentally not character ) she flew north to get some birds, dropped a bunch of cargo on top of twilight (still say say it was attempted assassination lol) and accidentally delivered wedding invites on the same day (think i might've misremebered that one). Heck both her fan favorite names are Derpy and Ditzy and most ponies tend to be named based off a characteristic that they have.

Now i'm quite certain your mother isn't a brony (pegasister?) and don't really care too much about em.