Why isn't this "Elle ne sait pas rien sur ta famille"? Does the "rien" take the place of the "pas"?
Yes : http://www.bertrandboutin.ca/Folder_151_Grammaire/O_a_la_negation.htm
can sur be replaced with de here? ie she knows nothing of your family
Did you notice that if you use connaitre it is sur and if you used savoir it is de? Interesting. Perhaps it is just idiom - we need someone French to tell us!
MWill22 I thought the same