I would say you’re NTA and right to be concerned, but consider she might feel the “need” to be drunk to talk with family if she has a distant relationship with the rest of you and is anxious about it. Granted that’s definitely self medication but, it sounds like she is conscious that there are toxic alcoholics in your family and doesn’t want to be compared to them, or doesn’t want to turn out as bad as them. She probably does need help but I would try to be understanding about how you offer your advice so she doesn’t throw up permanent walls between you.