Translation:She writes about the birthday of the girl.
Geboortedag specifically refers to the day you were born, whereas verjaardag refers to the anniversary of it.
I would see it this way: Geboortedag is "Date of birth" and Verjaardag is "birthday"
Geboortedag is actually also translated as birthday.
But as Wicketd said:
Geboortedag refers to the day you were born;
Verjaardag is the day where you celebrate your anniversary.
Conclusion: In English, a birthday can mean the day you were born or the anniversary. In Dutch, you got two separate words for those things.
Not quite the same. That would be "de geboortedatum" and then you wouldn't be writing about the actual event but about what else happened on that date and who else has their birthday on that particular day.
For me the best translation is "She is writing about the day the girl was born" but that gets marked as incorrect :(
Interesting that the Dutch way of saying this is so similar to the romance languages.
I really don't understand why my answer 'she writes about the date of birth of the girl' was marked wrong - and the 'correct' answer was given as 'she writes about the day of birth of the girl', especially as 'date of birth' was accepted a couple of items earlier - and in view of the discussion on this page and Yruzz's comment above
Date of birth = geboortedatum, which is the word that is used in the other sentence in this skill.
Also date of birth has not been accepted in the last 3 years for this sentence.