@ Jalan: It just means the person has flawless English, ie, they speak it like a native person. One dialect is not more "perfect" or "correct" than the other, despite the opinions of some. :-)
@ Peachey: I think we're encountering more dialectal variations between what you're used to hearing and what I'm used to hearing. :-) It's perfectly OK to say "she speaks perfect English." You'll see it in personnel reviews, books, discussions, etc. It's just like saying "fluent English" instead of "English fluently."
@ roi g: Yes, cowboy. :-)