I thought her name was "Ditzy-Doo" at one point, too. I mean, I didn't see the point of that scene, either--like, if Ponyville trusts her to be the mail carrier, one would think she'd be more competent than that. (/overanalyzing)

It's probably really disappointing because the show seems to have such a good track record otherwise--like, "come on, you're better than this."