Hi, katwats, welcome to PsychCentral (PC). I can see why you want to keep your sister at arms length and don't blame you.

I don't think anyone else, even if she had someone she "respected" could tell her anything that could change her in the telling; sounds like she needs real, concrete help. I don't think you are ever going to be able to have a good, adult relationship with her (in this lifetime).

I would downscale what you "want" to give/receive from her; knowing her drama, I'd try to drama proof myself so that it did not affect me as it has in the past, then she can be her "self" however. I would make sure you have boundaries (not high or smoking when with you, etc.) and just remember who you are and what you want rather than let her problems assault you. At the moment, Facebook is great :-) so just be pleasant but if she wants more than you want to give, tell her that; she can have all the excuses or ugliness she wants but not with you. She cannot assail your own feelings/boundaries which you have for your own reasons. There is no "right"/"wrong" about a relationship, just what we'd like/not like. You love your sister but doesn't sound like you necessarily like her. That's okay! You didn't choose her for your friend so you don't have to like her and want to be around her.