Note that Patient 31 is only the index case that caused the thousand-person cluster to be discovered, she's almost certainly not the cause of it despite various media reports that try and make it look that way. She had no recent overseas travel and no contact with known cases, I don't think anyone knows how she got it, and apparently she didn't even meet testing criteria and only got tested because some doctor ignored them on a hunch.
She probably wasn't even the first person in the Shincheonji Church in Daegu to be infected. The timeline of her infection is just too late compared to the cases at the hospital in Cheongdo potentially tied to other church members, most of the membership is much younger than her and therefore likely to display mild or no symptoms, and some of them had in fact travelled to China. If anything, it seems likely that she caught it from there rather than the other way around.
She probably wasn't even the first person in the Shincheonji Church in Daegu to be infected. The timeline of her infection is just too late compared to the cases at the hospital in Cheongdo potentially tied to other church members, most of the membership is much younger than her and therefore likely to display mild or no symptoms, and some of them had in fact travelled to China. If anything, it seems likely that she caught it from there rather than the other way around.