During the K1 Visa Attorneys process It is 100% the consular officer's prerogative to allow or disallow you in the interview room. In all cases your participation is not required or desired unless the officer asks you something in particular. The purpose of these interviews is to judge the fitness of the foreigner for entry/residence in the US and to satisfy the examining officer that the foreigner is entering into the arrangement with full knowledge and free will. If you come on too strong and 'eager" it could look 'fishy" to the officer. But if you are honest the process should go smoothly.