Threaten her with the pretense of firing her
From Create Your Own Story
'I'm afraid it has to come to this, but if I am the master, and you the maid. If you do not comply, then I will have no choice but to ask you to leave my service', you assert.
Marie looks surprised, but more so hurt (which makes you feel all the worse inside), but that soon changes into anger. She walks up to you and soundly slaps you.
'You are scum, nothing at all like your predecessors, I would gladly leave then serve you, a man who would force himself on others'. Then soundly turning on her heel, she storms out.
You stand there shocked and alone, not thinking she would actually consider leaving, maybe this was a mistake...