Are you serious? She's making $70k a month What the fuck does she need a high school degree for? That would be a complete waste of time and energy at this point in trying to run her business. And if her site is useless in 3 years, she can invest the large sums of money she is making into other enterprises. And if she really fucks up and blows all her money, she could go to college. You don't need a high school diploma to go to college.
That's like saying an athlete is stupid for going to the pros instead of staying in school. Make the money while you have that kind of an opportunity. You can always go back to school.
One more note - I'm from Detroit just like her, and there are plenty of people around here with college degrees that can't even find work (let alone just a high school diploma). Our economy around here is fucked thanks to the auto industry. Make it however you can.