I enjoyed this it's decent
It's seems that MC was always a pure girl even when she was a spoilt brat. I mean even a beautiful poor woman can end up as a trophy wife of some rich man, yet she apparently she let guys use her until she was past her 'prime'
the only thing I dislike is that she isn't using her current wealth to generate even more wealth and help those around them, I know it's more dramatic to invent healthy food to save the bento shop than simply loan the glasses girl some money to buy the ingredients. but I guess it's because she is quite pure.
If MC was a smarter she would nudge her father to invest in companies that are still afloat even in 2019, Apple is the obvious choice, Toyota and Honda are some domestic brands that are quite stable. put some money into trust funds, and US bonds (or whatever the JP equivalent is)
if she needed to get better at school she could easily pay for a private tutor/top tier cram school
But I guess something like that wouldn't make for an interesting story