If I remember correctly, speculation pointed out that Rabiane was trapped in a dream like state after fighting the Priest Nightmare. Even the farm stage and the clone stage were supposed to be but part of her own nightmare. It would make sense given the 4 tries you get against the final boss before game over, Rabiane becomes the mother of a new generation of Abominations. However, the swamp baby of the second game was born in complete different cincumstances, just like the tutorial boss and the gravedigger, so a demonic infestation is more likely due to Rabiane being trapped or indisposed to complete the job of her fellow sisters.
There is also the fact that Kessaria and this village of the second game are different, so different outbreaks of the Abominations are a possibility, with the entire kingdom or whatever facing incursions from the horrors in different locations and the Sisterhood pretty much overextended as a result.
And wow, I just made all of this for a game that does not give a lot of information, kind of like this freedom given by the developers.