My mother is a good example of a mature INFJ and a woman whom I will call EIOKILU (aka Everything Is OK, I Love You) is a good example of an immature INFJ.
My mother trained me in social nicities and how to get along with people. I don't agree with all of her methods but she certainly knew people (highly respected and liked by everyone who knows her) and her training helped me a great deal. Like every INFJ I know my mother puts a great deal of value on helping others and she is good at saying just the right thing. She looks at interpersonal and personal issues from a variety of different perspectives to find new and useful solutions. She is a people fixer. She is the person people come to to get things done and fix people problems. As a result she often ends up (accidentally) in charge of things. While she is good at this and seems to like it, I think she also finds it very stressful. It can be hard to tell when she's stressed though since she's good at keeping 'face'. When she gets stressed she will have uncharacteristic negative emotional displays (ie crying or accusations of lack of caring), fuss endlessly over details, and become meddling or controlling. Things that stress her include: over-extending herself on behalf of others, others demanding too much of her, and (I think) problems she thinks she should fix for people which she can't fix or which she's been told to not fix. Overall, she's likable, caring, capable, and people trust her judgement.
EIOKILU is likeable and cheerful and warm when you first meet her. She will be very interested in you and even if she doesn't like you it is unlikely that you will know it. She will smile at you until her stress level gets too high then she will blow up. In the long term, you will eventually learn that her attitude will change periodically from "I am totally in control of my life and can do anything" to "the world is out to get me, I'm doomed". She invests her whole future and well being in whatever she is into right now. All or nothing. The way she does it encourages you to care for her and encourage her... until you realize that she is doing most of it to herself and can't seem to talk about anything without relating it back to herself. She's conflict avoidant (until she blows up), passive-aggressive, with a very external loci of control, complains endlessly, and she idealizes overly. She will do what feels good right now even when she knows it is bad for her and justifies it as being out of her control.
When I brought problems in our relationship to her attention I got the "Everything is OK, I love you" with a side order of "I understand" and a full gluttony of justification, excuses, and professions of caring. I gave her a small list of what I needed in order to stay in the friendship, she promised to do them then disappeared for months. I walked. She occassionally whines to mutual friends about missing me and how I don't call her anymore (she doesn't call me).
