Can you clarify these questions to me? Did you mean how will your own jealousy affect your own life? Or are you talking about the INFJ friend?
I've dabbled in creative pursuits, and in the end, writing stuck to me. It defines me as who I am in the larger picture, and within my families and social circles, I am the author of the group. I love to write, writing has always been my endeavor and my escape. I don't think I've ever felt jealous of other writers, but I feel mostly inspired and in awe of their skills, and try to hone my own so that I can better myself.
I get jealous when it comes to the matters of the heart. I've definitely gotten better the more older I get, but I still get the green eyes whenever my husband looks at another woman. I will start to wonder what she's got that I don't have, and if I should emulate her so that my husband will become more satisfied with what he has at home. And then I kinda have to think, well, nothing is going to stop a man from looking, so might as well just be the best version I can be of myself, and that always works out. ;p I take love very seriously. Maybe I'm a love addict.
For you and your friend.. just do the best you can. You two have unique abilities that should be focused on bettering rather than comparing to other artists, because really, every body has something uniquely good about them and their creations, and that's a beautiful thing. They say that the best place an artist can be themselves, is in nature. Why don't you take a nice trip in the woods and maybe rent a cottage for a week or two? Just to get a real feeling of true solitude and let your thoughts cave in on you and you can let your own ideas flourish from the beauty that is seen and felt in nature.
Being a woman can be hard sometimes. Really. (;
Sometimes, a nice day at the spa, coupled with somebody doing my hair and making me look pretty, can take my self esteem up several notches. Remember what I said above: Every body has something uniquely wonderful about themselves. Once you enhance that, you'll feel a lot better. Trust me.
You should check out my private blog, titled "Journey to Self Love", I wrote about the therapy in a form of a workbook. I highly recommend it.
Best of luck!