If I were at your (knock knock) place, i would have asked the maid directly in a very humble and polite manner about her suspicious activities. Being her sponsor or guardian it is the duty to keep an eye on her's suspicious activities and try to make her understand that the things she is doing is not correct. Make her understand that she is married and is responsible for her family back in her country.

Put yourself in Knock knock shoes and then try to find the solution...