I can see that this is really frustrating. And it's clear that you've been more than patient with her. 3-4 hours late routinely? That sounds pretty extreme.
I've known similar stories, sometimes involving people close to myself. The most natural thing in the world is to want to help them and to take them at their word. There's danger in that though, because if you get to close their problems have a way of becoming your problems.
Sadly I've often found that try as we might, you simply can't help these people. All you end up doing is enabling them. Ultimately, they need to help themselves.