When jealousy strikes us it is important to look at our insecurities within the relationship. What are the things about the relationship that worry us? What are the things that we can change within ourselves? We have power over ourselves and the changes we make in our lives. We do not have the right or power to change someone else. They are not our moral responsibility. Use the jealousy to make yourself a better person and to strengthen your relationship.
Sometimes jealousy is a result of having been hurt in the present or past relationships. If one's mate cheats, lies, sneaks or has secrets then trust issues have been seriously violated. When new circumstances arise and trust is already broken it is only natural to become jealous and insecure about the relationship. Love is not a one way street. You should not have to fight to keep the person that you love. If you cannot trust them, then perhaps you're in a relationship of dependency and not love. Sit back and think about it and make the best choices.
Girls won't get jealous without a valid reason. Who started it?