Hello Makenzie. Yes, it's perfectly correct! You can also say "soy china", it's simpler but correct. Remember the difference between "China", the country and "china", the person from the country. Pay attention to the capital letters.

"I'm a chinese girl" se traduce "Yo soy una chica china" "Yo soy una chica de China" seria "I'm a girl from China".

If you want the strict translation to that sentence, it would be: "yo soy una chica china", but I think "soy china" or "soy una chica de China" sounds better.