She said to him, How can you say, I love you, when your heart is not with me? you have mocked me these three times, and have not told me in which your great strength lies.
The fact that Samson told Delilah to do something to his hair (Judges 16:13) suggests that he was giving her a clue to his strength. She did not pick this up but kept hounding him for his secret. Finally he gave in (Judges 16:17; cf. Judges 14:17).