Does shaving peach fuzz actually make it grow back darker? I'm a girl.

Not really. It does not. What it can do is shape the ends of the hairs so that they are blunted and may catch more light, becoming more visible. But the hairs do not grow in darker, or thicker.
? What exactly is a peach fuzz? Try using accurate words and descriptions - cannot help if you use teen language or slang.