Does your sister’s drug addiction affect your daughter? how does your sister’s life affect your daughter? Surely, it is something you could teach your daughter against.
Does it motivate your sister to not use heroin, and that is why you are are doing it? If so, family never can compare to addiction.
Are you fighting a battle using your daughter as fodder when a chlld cannot understand addiction in any form?
That is not understanding, or helping. Another stategy is needed to help your sister’s addiction.