That's the sort of reply someone who is ignorant, or doesn't want to appear so, would have.
I live in Florida so I see a lot of hillbilly rednecks with this stupid thing on their trucks and whatnot all the time. It's mostly toted around by racist rednecks and it represents a lot of bad things to people.
That is the flag that the south (for those not part of the states, that's the southern U.S.) wanted to secede from the union and be their own thing. There were many reasons they wanted to do this but the big one most people remember is slavery. A simple way of putting the civil war, though it is not just these two points, is that the North wanted to abolish slaves, and the south wanted to keep them. Watch the movie "Glory". Totally sweet.
Some people will claim it's "southern pride" or some other stupid thing, but to most people in the states it is just idiocy.
Can't be too harsh on her though, she is 13. When I was in elementary school I drew swastakas thinking they looked cool. Not knowing what it represented.