My little sisters entire life my parents not only spoiled her ridiculously but she also has never faced consequences. Seriously it’s like we had two different sets of parents growing up. She was/is impossible to deal with and has been since she was 4 years old. Instead of banding together to coparent my parents fed into it even more always trying to one up the other so if she was bad for my mom instead of being grounded or in trouble my dad would go get her and vice versa. I’ve said for years to them that she needs help but they had always said “she’ll grow out of it” though not sure how when all they’ve reinforced her entire life is she just has to scream and throw a fit to get her way.

On top of this learned bad behaviour it is very obvious my sister has severe mental health issues (I’ve got a long family line of mental health issues and I do believe she has borderline personality disorder). My parents never took her to see psychiatrist or anything when she was younger because again they believed she’d grow out of this behaviour. Well now it’s gotten her to the point where she is in trouble with the law.

Please give me advice on how to convince her to go get herself help.. unfortunately she is 18 therefore has to be the one to do it we can’t force her but I’m just at a loss...