Did I miss a scene?
One minute she gets blasted with an arrow, falls down a cliff and we see her extremely wounded on the ground.
1 episode later, she's chilling out just fine :S
I'm gonna go with magic.
"Breadsticks. For the mouth part of your face."
Well we see her wake up, and she's clearly injured. Then after the spell we don't see her till the next episode, and around a few days later (it would take them a while to get Ariadne back to Atlantis, and then for Jason to get to the Grey Sisters, and then the temple of Hecate).
My best guess, she was able to recover enough to manage to either crawl or walk out of the cavern, where her loyal forces were waiting, who immediately treated her wounds (as an army they're bound to have a doctor or some medical supplies).
I grant you its a bit of a fast recovery, but don't forget she's also touched by the gods, as is Jason. And its shown that has enhanced Jason's physical abilities and endurance quite a bit. By logic it should do the same to Pasiphae (its just as she's older and less active not to the same extent) making it possible.