If she notices that the cast attempt has failed, she'll retry every 10 seconds, or that's what it's supposed to do.
However, sometimes it can't tell when the skill has failed to cast due to the -_-ty excuse for an API we get to interact with the game through.
Also, it has a 1 cell range, and as mentioned above, it's easy to mess up with position bugging (homun's see position bug just like players do, only worse, because they have all sorts of other movement issues). When I had it not waiting 10 seconds to try again, it could get bugged up if owner was surrounded by monsters, and just watch owner die while trying and failing to get in PK range, instead of giving up and trying to kill the monsters so that it can get to the owner.