Earlier a post went up pointing out that The Last Roundup was released on iTunes finally. Sadly, it looks like she was actually modified. Her voice is different, and Rainbow Dash no longer names her.
This was in the SD version, I am not sure if the HD on my laptop is different. I am currently re-downloading it in HD To double check on my computer.
You can find the new Derpy after the break.
UPDATE: Both versions of the episode have been modified.
UPDATE 2: As a reminder, The Friendship Express DVD is untouched, Derpy is still Derpy (At least in the ones we got, which are pretty much the same as far as we know)