Since Friends became an international sensation, and was also popular beyond all belief in the Netherlands, I feel the production team could have done so much better on this little character. (The way you write her name isn't really the way we write it in the Netherlands we would write Marga, without the 'h'.) But she could have used the typical Dutch 'g'or 'ch' sound to make it sound Dutch.
She doesn't even pronounce her own name in a typically Dutch manner. She sounds, and even looks much more like a Russian, Ukraine or Belarusian woman. Even Joey's failed attempts of speaking French in 'The one where Joey speaks French' resemble the French language more than what this actress is trying to achieve. The actress portraying Margha obviously didn't do her homework. The girl speaks with a very heavy accent which unfortunately doesn't resemble the Dutch language or a Dutch accent at all. Margha, a Dutch girl appears while the group is playing a game of Football. Language accuracy can be a tricky thing, which is definitely the case in this episode.