What does it mean when you had a friend that was close to you than she became to change and become envious towards you?

let's understand what jealousy is as you said she is envious of you. 

Jealousy comes from dependence. The one who is not dependent cannot be jealous. The one who is his own master cannot be jealous. To be jealous means that I have accepted somebody as my master and now I want this master to remain with me. If he goes to someone else, then I feel a certain pain, and this pain is called 'jealousy'. 

The absence of 'I' is the root of jealousy and anger. This 'we', is the cumulative mind, the collective mind, the social mind, the comparative mind that lives in 'we', that lives in a tribe. Jealousy cannot be there without 'the other'. Jealousy is born out of comparison. Jealousy is born form a mind in which many, many are living. 

To say that there are many, means that they are different entities. And to say that there are different entities, means you have already compared them. Can you say that 'X' is different from 'Y' without comparing 'X' and 'Y'? 'We' means that different entities are present. And whenever there are different things, there would definitely be comparison and hence, jealousy. When the mind does not know the infinite and there are not many infinities, there cannot be many infinities, there is only one infinity. 

Friend by definition is a well-wisher. A friend by definition is a man who would celebrate if you are improving. Not a man who would be jealous and irritated seeing you walk the path of liberation. He is not a friend at all. But don't condemn him, because if he is not a friend to you, firstly he is not even a friend to himself! He is his own enemy, how can he be a friend to you? 

We make friends with so many people, without even asking, "Is that fellow a friend to himself first?" He is his own enemy, how can he be my friend? The one who does not know what is good for him, how will he know or like what is good for you? He is bound to resent it. How can you give importance to their resentment? 

These are the excerpts from my blog prashantadvait.com which contain more such articles which would give you more clarity on this. I invite you to visit them for further clarity.

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