Her assault(s) on you do not provide legal grounds to terminate the contract: they are wholly separate matters. As long as she complies with her obligatons under the contract (e.g. does whatever she is supposed to), you remain obligated to the agreement. Only if she breaches her obligations would you have grounds to terminate the contract. You can, of course, press charges for the assault; possibly seek a protective order; sue her for any injuries or medical costs (if any); etc.--but none of that invalidates the contract.