Charlie Sheen's Ex Brooke Mueller Hit With Drug and Assault Charges

Brooke has been charged with one count of having MORE than 4 grams of cocaine ... but prosecutors have covered themselves by filing another count -- possessing LESS than 4 grams, in case there's a problem with the measurement.

The amount of coke Brooke allegedly possessed determines the penalty ... if she's convicted. For more than 4 grams, Brooke could face 6 years in prison. For less than 4 grams, she'd face 18 months in prison.