@lolhahaha Sadly, it's not just the family, there have been spoilers that indicate that Penelope was abused all her life by pratically everyone, it's why in the flashback where she is picked by the family she is seen wearing bad clothes while looking disheveled despite her mother having been a merchant.
Just as the world goes out of it's way to appease Yvonne as the MC states, the main character will learn that Penelope had an amazingly abusive life since she was born, it didn't start out when she was 12 years old, the mansion just felt like life would finally turn around before the servants and everyone turned on her, i think that was when she snapped and stopped caring, and i think she didn't use her powers as a noble lady because...she wasn't raised as one until she was 12 and she is so used to being abused and no one caring about what she said that she didn't think it would work anyways, i think that is what was happening.
Yeah, according to spoilers and what is apparently revealed in the novel, Penelope had a really bad life and the game didn't even reveal half of it, and i think it's implied her abusive life is what made her become a villainess, why be nice to a world that just seems to exist to hurt her after all?