Why do white families sometimes have a mixture of hair and eye colors?

Short answer: Genetics.

This is presuming that the girl has done nothing to herself to change herself cosmetically (hair dye etc).

Black/brown eye colour come from having dominant genes. Blue/green eye colour comes from having both recessive genes. If the person had both a dominant and a  recessive gene then the dominant gene would be the gene expressed. Green eye colour is more rare as a recessive gene than blue. If you see an individual with black skin and light coloured hair, or black skin and light coloured eyes (presuming no contacts etc) then it's due to a genetic mutation that's expressed a recessive gene that would not normally be expressed. The gene expressed for the hair colour is completely separate to the gene expressed for any other body feature, such as hair.  It could also be that the type of hair that the family has is the type that lightens over time due to UV exposure, such as those individuals that start the summer with darker hair, spend time in the sun, then end the summer with natural highlights or lightened hair.

Rennie said all way cursed godthey try to turn back time  don’t let the out only his said not I love god all god alla god 

I dont know. but.....here is this: 

Melanesians of some islands are one of the few non-European peoples, and the only dark-skinned group of people outside Australia, known to have blond hair.

that might help a little; if u aren't from there and you're african/native american thats probably why

Blame genetics or your parents, like everyone else does when they realise they're stuck with traits that they hate.

Some people have variety of eye shades, even hair colours.  My dad started out with blond hair, but it became brunet by the time he was 20.

that's a mystery of the ages one never knows ever

Because they have different DNA. Each child gets different DNA from their parents. 

My dad has five siblings.  They go from very dark brown eyes to “Paul Newman” blue eyes. My dad has straight hair and most of his siblings have curly hair. 

Most Caucasians have a lot of different ethic backgrounds in their family tree. Different traits come out.

People have been mixing since time began.

It's all genetics when it comes to hair and eye color. Darker hair and dark eye colors are more dominant, but if your family has any ligh

My sister has straight brown hair and blue eyes, while I have blonde curly hair and brown eyes. Both of our parents have brown hair and brown eyes. But our grandmothers had brown or blonde hair and blue eyes. My grandfather also had brown hair and blue eyes. 

It may not be because you're black, you would have to get a genetic test done (for example a DNA test from Ancestry) to see what makes up your genetics to prove that. 

Lots and lots of different genes. Black hair & brown are much more common & dominant traits.