I think people are being too harsh on you OP. First they say all kinds of things that misrepresent the reality of the friendship, tell you to self reflect, then you get criticised for being obsessive by looking back through the evidence to see if it's true.
Apparently if you don't agree with the perceptions of people who don't know the friendship and don't know you, and try to correct them, then you are criticised for 'not taking things on board', even if they are not factually accurate.
When you try to show people that this was a close and meaningful friendship with a lot of mutual support (and not as one-sided as other people are suggesting), you are accused of holding debts over the other person or basing the whole friendship on doing everything for her, neither of which seems accurate from what you've said.
It's obvious that this was a close and meaningful friendship, I mean 17 years is a lot, 4 years of contact since moving away, that is a strong friendship. Everything you've said suggests a strong friendship. Not everyone understands that long distance friendships can be close and meaningful. If you were texting every day for years and you both enjoyed that and were fulfilled by it, that is the kind of friendship it was. Just because other people rarely text their friends or don't bother with people who aren't there in person, doesn't mean that everyone is like that or that this is how all friendships should be.
I think anyone would be very upset at a sudden dropping off of contact with no explanation. Ghosting or fading out when you have been close like that is definitely a reason to be upset, cause for concern. I don't think it's a nice away to treat your close friends. People seem to be comparing this to a much more casual friendship, but imagine if someone you spend time with every day and seemed to be a pillar of support in your life suddenly just started avoiding you with no explanation - how would you feel? It does not make a difference that it's long distance, if this is how they sustained things for a long time.
And it seems you were right in your intuition that she was lying about the real reasons. It's good that she has now told you the truth and you can work towards something more sustainable in the future. I know how hard it can be when something like this happens, I hope that you are able to find some other friends so that it is not all so much on one person. I know that this has caused you to spiral emotionally, I hope you are able to get on an even keel soon. I don't normally comment but I felt like you were being very much misunderstood on this thread and I feel like I needed to offer some understanding and support.