Indeed it is. But I'd say someone who can master up to ten languages has a gift for learning languages. And unfortunately few possess that talent.
To most of us it's hard work and endless practise.
It's my impression that Mary hasn't been born with a gift for learning languages, or she would probably have picked up other languages by now, besides English and Danish and perhaps a little French.
That means she must have had to work and work hard to get where she is now.
That's also an accomplishment, eh?
However, there is a considerable difference between learning the basis of a language. I.e. grammar, spelling, correct pronounciaton and to master a language, with all the subtleties, dialects, slang, accents.
That's the difference between newsreader-English and English as spoken by people in the street.
It's when you can do crosswords at a reasonable level and when you can effortlessly understand and chat with people on the street that you can say that you truly master a language.