If you play the sub like she wants, she may get bored and dump you herself.
Maintain your independence at all costs. Not necessarily spinning plates (although keep girls keen), but the freedom to have time to yourself, see a movie alone etc, whenever you want. Keep her guessing but keep her sweet.
It doesn't matter how much cash a girl has, as a guy, I want my own thing. Spending someone else's money for my own pleasures feels unsatisfying. Still, obviously this chick is overloaded with dough and you can't just let some Josh or Stephen roll in and snap it up... and they will, in the blink of an eye.
Are you actually attracted to her?