Same thing happened with my friend and me. Every so often, when she's doing well, she contacts me to tell me so - and that's the only time I hear from her unless I bump into her in town. It's been five years this time.
I don't mind a bit. When we were teenagers she was a good friend to me when no-one else thought I was worth bothering with. She had problems of her own then and she's had plenty since, but we've always worked to the maxim 'you know where I am if you need me'. She's famously bad at not keeping in touch or telling me when events are happening, but that's her and I love her for it.
My very best friend - my cousin, in fact - lives 8000 miles away in the USA. I haven't seen him for three years. He has mental health issues that often make it impossible for him to rouse himself to write or phone me. Things happen to him that I only learn about through his mother. He doesn't get around to telling me for months and it frustrates me that I'm not able to support him when he needs it most. But again, that's him. Just knowing he exists and doesn't mean anything nasty by his apparent 'selfishness' is enough. What he values is that I don't mind his behaviour and can be a constant in his life at the times when everyone else gives up on him.
Maybe, indieanna, that's why your friend comes to you like this. Maybe she feels that whatever stupid, annoying thing she does, you will still love her. And isn't that what true friendship is about?