Remorse
"Sir, an encoded message has just gone out."
It's Michael's first mistake and may well be her last.
If Lorca had not already been planning on using Discovery against her, Michael would have delivered it to him nonetheless. Her transmission is a beacon, one that leads him to her heart, her inner softness.
How strange. Once, he would have scorned it as her weakness. But that would be hypocrisy, for, though he will never admit it to any but her, Lorca loves them too.
The difference between them is that his love will not stay his hand.