Although this doesn’t directly answer your question, here’s what I know from other people’s spoilers and the raw. Spoilers read at your own risk:
Spoilers:
Arth proposes to our mc soonish. And apparently Lilith’s mom is a transmigrator who abused Lilith to get her to follow the story perfectly so her mom could return to earth.
wowie that makes a lot things make sense, do you know why arth knew lilith in the first place? why did arth trust lilith not to hurt the MC?
I think it's because Payne is in love with Lilith and Arth was helping him, possibly because they're friends. It may have something to do with the face that Arth wants to put Payne on the throne instead of the current crown prince because I think that's what eventually happens. I'm not completely sure though. Here's where I originally got the spoilers, you can try looking further:
https://forum.novelupdates.com/threads/pet-of-the-villainess.91581/
Thank you! And I agree
im starting to get suspicious of arth i know he is planning something but whats with all the secrecy and his affiliation with lilith?! makes his 'plan' seem a bit sinister. maybe he is trying to back payne as king and lilith is in on it although that wouldnt explain her behaviour... or are lilith payne and arth from Earth and thats why lilith has a notebook similar to the one arth used to carry around?