V. Stiviano has just filed new legal docs in her war with Shelly Sterling -- claiming she NEVER slept with Donald Sterling ... 'cause he's into men and she was his beard.

TMZ Sports has obtained the lawsuit -- which Stiviano filed in response to Shelly's allegations that V. accepted cars and property from Donald that he didn't have the authority to give her.

In the new docs, Stiviano argues that the items in question were given to her in exchange for being Donald's "beard" -- and she insists Shelly knew about it.

Stiviano states ... she was "not ever a sexual partner of Donald T. Sterling" and "believes that [Sterling] is a homosexual and enjoys sexual acts and or sexual congress with males."