Jealousy, you know, is usually not an affair of causes. It is much more-how shall I say?-fundamental than that. Based on the knowledge that one's love is not returned. And so one goes on waiting, watching, expecting...that the loved one will turn to someone else.
Women can accept the fact that a man is a rotter, a swindler, a drug taker, a confirmed liar, and a general swine, without batting an eyelash, and without its impairing their affection for the brute in the least. Women are wonderful realists.
It is my experience that no one, in the course of conversation, can fail to give themselves away sooner or later. Everyone has an irresistible urge to talk about themselves.