OP. The post I'm quoting here is blunt and direct. It's also the kindest possible advice you could receive in the circumstances.
Your posts to the tune of 'I get it, I'm too needy, I must be a terrible person, lesson learned' etc are a combination of passive aggression, self-pity and manipulation. I'm sorry to call them so bluntly, but this is what they are. They are also, for any person who has been on the receiving end of emotionally abusive behaviour, a huge red flag. I'm not saying at all that you are an emotional abuser. But, nonetheless, these are some of the tactics they use. If this has come in any way as a surprise to you then it's worth doing some serious self-reflection as to why that's the case.
I can also say with a fair degree of confidence that if this is the way you interact in your friendships, then this alone is a clear reason why people are distancing themselves. It sucks people dry. Emotional vampirism, the psychologists sometimes call it. You say yourself you thought she 'cared' - perhaps at one time she did, but has reached the point where she now has nothing further to give. That's fair. No one owes us their friendship. What you need to do now is to respect her decision.
You can deny these issues and retreat into self-pity if you want to, but this isn't going to help you in any way. You've had lots of help on this thread but you seem to prefer to view that posters are simply being mean, in the same way you feel your friend has been mean. Neither is likely true.
I get it. Rejection isn't nice. It makes us feel horrible. But if you really want fulfilling, properly reciprocal friendships in the future, you'd be wise to take the well-meaning advice on this thread and try to unpick all this with the help of a therapist. Working on yourself is hard and forces you to face unpleasant truths. I know, I've done it. But the choice of whether to wallow in recrimination and self-pity, or foster a happier future with emotionally healthy friendships, is yours alone to make.
You've been handed an opportunity here of learning from your experience. Don't waste it.