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At the end of the day; both parties get what they want. Is it emotionally or psychologically healthy.... probably not. But then again people do a lot of unhealthy things all the time.
The other thing I will add is that this kind of situation is great for the richer party. They get all the benefits and when they are tired of their play-thing, they simply cancel the credit cards and the car service and move on.
One would hope that said girl has been saving most of her cash, and making the most use of the networking opportunities she has been afforded.