Well, AJ is dragging Dash into a farrier's office, where she'll get her hooves trimmed, a process that involves lots of cutting and fracturing. And based on the show, we know Dash doesn't like having ponies touch her hooves, hence her fear.
It took me a moment to catch the Ponyville Confidential reference. There aren't enough works that play on the comedic potential of Dash's hoof-touching fear.