Nobody is denying that northern Virginia is part of the DC Metro area. That doesn't make it magically not Virginian any more than it makes Prince George's count

Nobody is denying that northern Virginia is part of the DC Metro area. That doesn't make it magically not Virginian any more than it makes Prince George's county, etc. not part of Maryland. Your friends would say they were from DC, or the DC area, because that is accurate. Also, DC being a notable city, this is more recognizable to folks not from around here. I say I'm from Virginia because that's accurate and just as recognizable. But some people like to say they're from a big city even if they grew up far outside of it ... to each their own. Growing up in DC is a decidedly different experience from growing up in any part of Virginia and I'd find it disingenuous to claim either inaccurately. You are confusing two different things.