One other thing, since you still want to be her friend due to your long history with her, maybe you can just see her less often and hang out in a group with her since you know some of the same people.

That way you probably won't have to listen to all or her problems, or lies that much. Or just go to the movies with her, go out to eat, and change the subject if she starts talking about stuff that you know isn't true, or if she starts talking to much about herself, etc...

Just downgrade her a little to a casual friend if you don't want to cut her off completely. Hopefully she'll get the help that she needs and change for the better sooner or later.