I think I really agree with AThingInYourLife, and a lot of others. (I chose AThing because her post summed up things quite neatly).
I really feel for your friend but I had a strange thought as I read your thread: This is kind of like what bullying is, isn't it?
We're told that kids bully other kids because of some lack in the bully, and they pick on a vulnerable kid, and they have an opportunity to continue bullying that other kid, often with the support of others.
It hit me that that's what's going on here. Your friend is in a grim place, she;s making herself feel better by hitting out at you. She's doing that by hitting you where it hurts: your care for her; your feeling of friendship with her. She's able to do it because you care for her. And the fact that another friend has 'phoned you up to tell you is a bit ...
. It means she's actually getting other people, mutual friends, on board.
It kind of doesn't look like bullying - but then, even in schools, it often doesn't, unless there is actual bruising - because your friend's pain is real, and what she's doing seems quite reasonable. But the pain you are now feeling is very real.
Who deals with their own pain by making sure someone else, especially a friend, is forced down into the pain? Kids, really. And adults who still have some figuring out of life to do. And people who enjoy that kind of thing. And people who are in a lot of emotional pain and not thinking rationally, I guess.
I am so sorry about your friendship. And I feel for your friend. I hope that she learns to accept that life sometimes does not follow our plans, and we have to relinquish some of our wishes. And that, even so, it is still a wonderful thing to live. I hope she learns that destruction of others is not the best way to deal with our own losses. But I also feel that you might permit yourself a small acknowledgment that she is perhaps not the best friend you ever had or might have.