Your mom is acting like that because she overly identifies with your sister, to the point of having lost herself. Whatever happens to your sister, she internalizes it just as if it's happening to her. Even worse, when your sister hits her bottom and she will, your mom may not hit her own personal bottom.
It's often said that codies are just as sick as those they enable, if not sicker, and it's true. Please do what you can for those kids that does not involve enabling your sister. Read the ACOA forum here for an eye opener on how children are devastatingly affected by their addict parents. Get yourself to a 12 step meeting and learn how to deal with your addicted loved ones. Your mom is addicted, too
