I mean she has a stable REALLY HIGH income consistently coming in, she’s allowed to be frivolous with her spending. That said, she should really be setting aside X amount every month to save (and earn interest even if just a little) for a rainy day. You never know what’s going to happen in the future. I think that’s the only advice he should have given her. He even could have used himself as an excuse (and asked that he saved for him or gave him X money a month that he could save himself). That way if she ever spent too much or her source(s) of income failed, he could step in and help (and she couldn’t stop him from using what was now HIS money).
I am still really curious about her source(s) of income. She said she owns the building (unless you can own just one apartment), so I’m assuming she’s the landlord, but even then that’s not nearly enough money to make up for all her expenses each month. She has to have either one really high earning source of income or multiple really good sources of income (I’d say at least 3). Maybe’s she’s investing, in the stock market, or currency exchange. I really can’t think of other ways she’d make a ton of money (like “I don’t care how much I spend” amounts) each month. But, hey I’m not making a ton of money so obviously I don’t know how people who are do. She’s always with him, so it has to be narrowed down to something where you don’t have to go in a lot (unless she’s doing something while he sleeps). Idk. This will be one of the biggest mysteries of the series (along with, basically everything else about her).