Hello! Thank you, so nice to hear you enjoyed the game! Heartening too as we are still planning some future improvements.
SPOILERS
A few things are up for players' interpretation here: 1) What is the place they went to (Is it really Hell, or a hellish space that was created?) 2) Was that person really MC's mother, 3) If so, is she a demoness or perhaps she was posing as one? If not, why would the demoness get involved? Perhaps out of her own reasons - pity or disgust and wanting nothing to do with humans for example.
You have your own ideas and thoughts about it, I'm sure : ) Some things that are definitive - yes, MC is immune to the plague, and her mother did die of it . Other than that, things are kind of up to interpretation.
If you'd like to share, let me know which was your favorite route and why! It helps to know what resonates with players. Thank you again!