in italian "sorella germana" is
"Persona di sesso femminile nata dallo stesso padre e dalla stessa madre (sorella germana)"
"someone, female sex, born by the same father and the same mather"
soror is more general. Even by different father, or different mother [but even with same parents too!!!!]
In Latin "soror" was the most common word (used quite in all the occasion)