This is a very hard situation to be in, feels like a pending break up right?
Well, there are some things that you need to remember,
i deal with people all the time who have freinds that have addiction problems, such as gambeling.
and this is kind of like that. You need to remember, that alot if not all of that anger is not your friend youve known and loved for years, but is the illness that has affected her. You need to look at the history of your relationship, and decide, is this really the way shes always been, with one exscuse after another, or is this acctuley something that started when the depression started. Then if youdecide that its the depression that started it, then you need to be very careful about how yougo about handeling it. I do agree with cajun that whole do whats best for you attitude, but you also owe it to your friendship, to make sure your not to hard or drastic on your firend.
So i would just try to spend more time doing other things, like reading, or try starting a new hobbie, so when she calls round,you can say your busy with something. Because that way, you wont be lieing, and you will still have that friendship around for when you both get better.
But please, please, dont forget about your friend, you 2 have been together foralong time, dont let her slip through the cracks, because once that happens, its all over. And altho it seems like it sometimes, depression wont last forever, but your friendship could.
good luck to you and i hope it all works out for you.