Anyone who could afford to leave would do so, since futures with a batshit insane queen who bombs vast areas of her own city are not ones that merchants and property owners thrive in.
Once those people leave, the people they support will start to suffer.
Once they suffer, they either cause mass poverty, crime and unrest, or they find a way to fuck off elsewhere.
Once that happens, generation of money and produce starts to wane.
Once that happens, she loses her ability to fund her methods of suppression.
While it's possible for her to initially crush any unrest, it would cause mass expenditure to do so in the long run, and that's not counting the fact that she needs her army to fight off the legions of people she's pissed off.