From what you've written, it could actually be envy that you've managed to move on so well with your life and she hasn't, she may feel that keeping you as a friend might actually be bad for her nowadays? I'm not saying this definitely is the case, but it sounds like it. Also when your life has picked up she may have perceived at some point (falsely possibly) that you might have abandoned her and now she is wanting you to stay away. Just guesswork from what you've written. I do hope something sorts out between you two, I know what it's like to feel abandoned by people you think are your close friends, but sometimes the answer is innocent.