I think "sappiamo" is more for skills or abilities ('I know Italian' - I can speak and understand Italian) vs. conosciamo, which is knowing about or OF something ('I know Italian' - I know of the Italian language, I know what 'Italian' means, etc.)
Thats way too simplified. Conocere can also be for works of art, places, literature, etc.
Sapere is for facts and information
Conocere is for things you're familiar with. You can't sapere a book unless you memorized every single word.
What's wrong with "Non conosciamo alla ragazza"? You can perfectly translate "We do not know the girl" in spanish as "No conocemos a la chica" or "No conocemos la chica". Does this not happen in italian?