At this point Seth its about her only hope for a (semi) easy fix. She can always take it back to Lowe's if it doesn't work out. The drain is a duct, like any other duct if you keep pouring flow into it be it air or water, it will take the path of least resistance. Assuming is it clear and open and the vent pipe is inserted as far as they can get it in to the drain, if they can seal it up using some insulation of sorts to make it tight it's may just work.
Definitely worth a shot IMHO.
Definitely worth a shot IMHO.