It doesn't prove that girls are evil at all. It is a formula for working out how evil individual girls are by basing it on two variables (time and money) and being perspective based on top of that.
If a girl takes up none of your time and none of your money, which I imagine most girls in the world don't, then said girls can't be evil from your perspective.
Therefore girls are not necessarily evil.
...
It doesn't work anyway as I spend far more money and time on my girlfriend than I do Hillary Clinton, but I like my girlfriend a whole lot more lol.