I agree, this person is not suitable for the job. If you are not quite ready to say this you might try sitting her down and telling her the facts- that she will NOT get the job if she is NOT prepared to do things your way, that her getting the job depends solely on you, and see if this makes her buck her ideas up. If not, she will have to go back to the agency. Either way you need to tell your Boss the whole truth so he knows exactly what is going on.