I hate to admit it but I've done the same thing before (and still do on occasion). I'd like comfort from my family but when they try the only way they know how, I push them away thinking at times that it's not genuine or why burden them with trying to help me or some other stupid notion. It just drives them away further. I'm not really sure how to get through to your sister (as I don't know how to help myself and family with it myself) but it's just a manifestation of the illness I think. Sorry I don't have any more pearl of wisdom for you. I know it must be so taxing for you and admire that you still try to help with what you can.