Viv's knowledge of theology could most charitably be described as, "non-existent".
If they were in Purgatory, I think you run into a harder problem with redemption, in that these are people that are supposedly on the razor's edge between salvation and damnation, and most of the characters in the show absolutely belong on an express elevator straight to perdition.
Also, at least according to Catholic teaching, Purgatory isn't like a third realm you can just chill in, and head up or down. It's a process where the souls of the saved have their sins purged (hence the name) so that they can enter into Heaven and behold the beatific vision. To quote the Catechism.
All who die in God’s grace, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven (1030).
While works like Dante talk about it taking a long time (possibly millennia for some souls) there's nothing AFAIK that Catholic teaching says that it necessarily is incredibly long, though the reason its often seen as a form of suffering comes from I Corinthians.
For no other foundation can any one lay than that which is laid, which is Jesus Christ. Now if any one builds on the foundation with gold, silver, precious stones, wood, hay, stubble—each man’s work will become manifest; for the Day will disclose it, because it will be revealed with fire, and the fire will test what sort of work each one has done. If the work which any man has built on the foundation survives, he will receive a reward. If any man’s work is burned up, he will suffer loss, though he himself will be saved, but only as through fire.
