Hi Sarahsweets!
Thank you for your time. I visit this thread everyday because each and every response has been really helpful to me. To reply to a part of your comment:
He doesnt give her money does he? Maybe I missed that part? I feel like if the OP makes it clear to his mom that she is enabling his sister by doing this and sets the boundaries for what he would do if she continues then he is not in any way responsible for his mom's finances.
You are correct, I don’t give her money. My mom does. In the past I had made it clear that my mom is enabling my sister by doing so. The result was that my mom told sis something like 'Geez I really want to help you out but I can't because Britedark told me not to and said that this is enabling behaviour'. Then both dismissed it as mere spite on my part. I know I am not responsible for cleaning up my mom's mess but I worry about her nonetheless.
Also, after I read your comment I realized that I haven't identified myself! I am a 37 yo woman. Please don't apologise for assuming I am a man. It was entirely my fault