She is your best friend. You spend hours together laughing and sharing your deepest secrets. Then one day she makes some offhanded remark about how that guy you liked rejected you because you aren't smart enough. Where did that come from? Then your co-worker steals your presentation idea, passes it off as her own and starts spreading lies about you around the office. Why? She seems like a strong, intelligent, independent woman. What is going on?
We have all been there at one point or another.
Someone we thought was our friend or trusted confidant stabs us in the back, sometimes gently, sometimes hard. Maybe it was over a guy, a job promotion or just over something silly. We blame ourselves, wondering what we did wrong. Did we say something offensive? Were we incompetent at work? The truth is, you were simply seen as a rival, through no fault of your own. Still, it is painful to lose a friend or close colleague to jealousy. Jealousy hurts.
Jealousy and envy are defined differently.
Jealousy is the fear of losing something you already own to a perceived rival, such as a boyfriend or position at work, whereas envy is simply wanting something somebody else has. However, increasingly the two words have become interchangeable in people’s minds. Both jealousy and envy are born from places of fear and insecurity. Jealous women can be particularly hard to deal with and can truly do real damage, therefore it is wise to tread lightly when dealing with one. 
Women tend to be better at reading people and less outwardly abusive than men, so they have become very good at getting in little “digs” at other women.
Try to see her point of view. In a way it is flattering that someone would be so affected by you. A woman who is jealous or envious of you is acting from a place of deprivation, of self-doubt. As much as you can, build her up. Make them aware of their own value. Try to help them get the thing that it is they want, as long as it is not something that is of value to you like your job or your boyfriend. If these things don’t work, well, then it is time to start limiting your time with them as much as possible.
Is Her Jealousy Justified?
We cannot say jealousy itself is "wrong." What can be wrong, however, is how we act on it. If you did indeed snatch up that guy she was falling for, or if you got your hands on the position you knew she had been seeking for so long, then of course she may feel jealous. This is a natural feeling and you should recognize that your actions, even if you don't feel they were wrong, were going to cause her pain. Look over the reasons she is jealous, and then look at your actions. Ask yourself, "how would I feel if this were reversed?". If you have responsibility in her pain, then now is the time to be humble about it and let her know that you understand her pain and her feelings. If her child struggles in school, while your child is the all-star, and you rub it in over and over, then if she winds up feeling jealous, guess who was the person who spawned it? Or if the jealousy is over her belief that you stole someone she had a romantic interest in, then this is going to be a very deep issue that will most likely require professional counseling to resolve. At the end of the day, if you have a friend who is jealous, this means your entire friendship is at risk, and for the sake of both of you, it should be dealt with, and the elephants on the table should be identified.
Be smart, too.
A jealous woman who is acting out in unhealthy ways may try to bring you down to her level. Don’t go there. Meet her bad behavior with good behavior so she can not say anything bad to others about you that would stand the test of truth. You can trust that she is looking for anything she can use against you. Beware the co-worker who pretends to be your friend to suck information out of you. She will use it against you later so watch what you say. Don’t gossip about others with her because, if she is already jealous of you, then you can be guaranteed that she will run and tell the person what you said. 
Now let’s be fair.
Have we not been jealous of another woman at some point, too? Maybe she was prettier, or had more friends, or she got that cool new job we were secretly hoping she wouldn’t get. You know how much you resented her in that moment. Is it not just as painful to be jealous of another woman as it is to be the recipient of jealousy?
Feeling jealous and acting jealous are two different things. You must be honest with yourself and admit it if you are feeling jealous. Acknowledge the feeling, but do not act harshly on it. Communication is almost never the wrong answer. If you communicate in an honest way, without venom or "digs", then you are doing the right thing. 
If you are feeling jealous of another woman, whether it be a friend, colleague or roommate, understand that you have value, too. Even though you may be longing for something they have or feeling as though life is unfair because they have something that you want and you don’t, that doesn't mean you don't have amazing qualities and traits that can shine brightly. Build up your own self-worth and dwell on your positive traits. Take stock of your blessings - you may just find that you have a lot to be envious of, too.
It is not a "bad thing" that she is beautiful, talented, highly esteemed, gets all the guys, is extremely intelligent, etc. Remember that her life is full of problems too, and she has many inner struggles as well. Perhaps if you took the time to get to know her, you would find that she is just as full of insecurities and, yes, the occasional bout of jealousy towards other women as you are. Who knows, you may even wind up with a closer friend.
 [“The Psychology of Jealousy and Envy” Peter Salovey, 1991. P. 27]
 [“Intolerance of Sexy Peers: Ingtrasexual Competition Among Women” Tracy Vaillancourt and Aanchal Sharma, 2011 https://app.box.com/s/rdthllpbpfuk0g2lqtdt]
 [“Jealousy is a Killer: How to Break Free From Your Jealous Feelings.” 2008 by Robert L. Leahy, Ph.D. in Anxiety Fileshttp://www.psychologytoday.com/blog/anxiety-files/200805/jealousy-is-killer-how-break-free-your-jealous-feelings]