"I write about the girl."
So "scrivere da [someone]" is incorrect and doesn't mean the same as "to write of [someone/something]" ("He wrote of her...") in English?
"Scrivo della ragazza" is better and less misunderstandable than "scrivo sulla ragazza"; other options to translate about would be "scrivo riguardo la ragazza", "scrivo circa la ragazza" and so on, but those are more formal.
@f.formica- can you explain how "scrivo sulla ragazza" could be misunderstood? Grazie!
The most immediate meaning of "scrivere su" is "write on"; "scrivo sul foglio di carta" could mean "I write about the sheet of paper", but it's much more commonly understood as "I write on the sheet of paper". So "scrivo sulla ragazza" evokes the image of a tattoo artist first. It would be different if there was an object: "scrivo un libro sulla ragazza" would be interpreted as "I write a book about the girl" without ambiguity.
I don't know about the Italian (I'm a native speaker of American English)- but I can tell you that "to write of" would be very formal and something you would see only in WRITING. Same goes for "to speak of". We would say "to speak ABOUT" or "to write ABOUT".
You mean the pronoun? That means "about it/him/her" rather than just "about": "Scrivo della (sulla) ragazza. Ne scrivo in un libro." -> "I write about the girl. I write about it (about her) in a book.".