I know some black poodles (well, any color really, but it's most obvious in blacks) can be prone to growing a lot of grey or white hairs mixed among their black hairs. In poodles it's called 'bad black', especially when it happens in young dogs as opposed to natural greying with age, and it's totally harmless, just not desirable in the show ring. I wouldn't be surprised if similar can happen in Porties.
Do you know what colors her parents were?
Do you know what colors her parents were?