Avoid enabling her behavior. If she insists that you text her every five minutes when you are out with your friends, tell her no. You don't have to be mean about it, but you do need to be firm. If you constantly placate her jealousy with reassurance and capitulation then she'll never have any reason to stop her behavior.

Ask her to wait until she's cooled down to express her jealousy. Anger, sadness and generally strong emotions can make things more difficult, so if you wait until things are calm and rational then it will be easier to talk about why she feels jealous.

Encourage her to do things that focus on her. An activity that only she likes, a night out with her friends, or anything that is fun but doesn't involve you will help. This will help her feel good about herself on her own, which will make her less dependent on her marriage for self-esteem and therefore less jealous.

Reassure her that you love her -- only her -- at unexpected times, rather than just when she becomes jealous. This will help build trust because she won't be able to think "you're just saying that because I'm accusing you." It will also deny her the reassurance that she gets from you defending yourself when she does become jealous, which will in turn encourage her to focus on the happiness the relationship itself gives her. Over time, this will boost her self-esteem and reduce her tendency towards jealousy.