Cultists are, in Lucy's admittedly limited experience, never a good thing.
For one thing, they're almost always worshipping something that she's pretty sure doesn't care, and for another, they're almost always planning to do something stupid about it.
Normally this would be neatly solvable by simply avoiding them; Lucy's pretty excited about the whole idea of being able to safely interact with people now, but that doesn't mean she wants to interact with the really inadvisable ones. Occasionally, however, they will be up to something really stupid and require interference.
She's pretty sure they successfully interfered. Wherever the hell they are now, she doesn't think what the cultists were trying to do was send them there.