The Man expected Arwen to be furious, not grateful. The twins must have done something, thinking to help him. Except that whatever they did was not helping since the Man wished to break up with their sister. Aragorn knew the golden Elf cared about him; though he could not pursue Lasgalen now, he wanted to be free to do so once the new recruit became proficient at combat. That would only be possible if the Man ended his game of courtship with the Evening Star.