I'd say race and money were a factor, but he wasn't sober and the hit and run resulted in the death of a human being. The girl should definitely be charged, but if he pulled in front of her and caused the accident, he's at blame too.
There are two factors at work here - money and race. He has a public defender because he doesn't have money. He spent three months in jail because he doesn't have money. Her family hired a "host of lawyers" (and a 17 year was driving a Yukon) because they probably have money. That's all clear.
His lack of money has NOTHING to do with what he was charged with. Her family's money probably has little to do with what she wasn't charged with. The charges are where the racism comes in, imo.