My sister is a shit show

Before I get into this shit show, let me explain my sister's background. Basically since she was 13 she has always been in a relationship, mostly toxic ones. She got married at 19 after only dating him for 5 months. She and her husband lived with our parents and myself for 3ish years before they separated(not divorced). They both cheated in the relationship and he did coke for a time. Not to mention my sister is an alcoholic. That whole time my sister only had a job for a year(non consecutive) and her husband spent all of the money he made before they could save up or pay rent to our parent.

She said (probably for the 2rd time in her life) that she was just going to be single for a while to learn to love herself. Well that lasted all of 6 months before she jumped into a year long relationship with another toxic man who fooled us all into believing he was perfect for her. That relationship ended and she once again swore that she was going to be single to learn to love herself. Then 2 months later she's in her first poly relationship which failed after a month and the couple she was with ended up breaking up too. Each time she got into a relationship she moved way to fast.

Well now my sister is 25. She went to Miami to supposedly go stay with her best friend, but she was likely at the house of this couple she met 6 months ago online. She's now it her second poly relationship. I know this because I asked her if she has ever met them irl and she said yes and that she stayed with them for a week. Meaning she lied once again to our parents.

This month she told them that she was going to Miami again cause a couple was having her over for a two month trail of nannying their 4 year old daughter. Which was again, a lie. This couple has a 14 year old daughter and the reason she is going is to be in a relationship with them because"they make me happy and my mental health is so much better with them", which she has said in every relationship she has ever been in.

So basically, she's going to live rent free with a sugar mama and daddy and their daughter after knowing them less than a year. She moved 4 hour drive to a strangers house. I made her tell me all the basic details of these people cause "when these people murder you I'll be able to tell our parents what your dumb ass did", but in less harsh words. She is still 100% dependent on them. No driver's license because she has at least a $400 fine. Doesn't help pay any bills, doesn't get her own food. Sits around all day when shr should be out looking for a job. Our parents are too soft on her because she's had anxiety and depression since she was 10.

I'm 4 years younger than her. I don't understand how she is so immature and irresponsible. I realize I didnt tell our whole life story so I'm probably going to get shit for judging her, but she makes the worst decisions. I could write a book about it, but this post is long enough and I dont need to be spending all my time thinking about her toxic ass