BOYFRIEND IS A SMOKER AND SELF DESTRUCTIVE?

My sister is in a relationship with a guy who is 24. She is 26. She met this guy through a common friend. He is a muslim who is half white.

He is younger than her (she had this idea she wouldn't date guys younger than her and always preferred older men but she overlooked this one and because he is a lot taller than her and she looks younger than him, she overlooked these facts) and he is actually of Pakistani descent (from his dad's side).

This guy is absoluetely drop dead gorgeous in looks (to my sister, he resembles Aladdin, all that long dark hair till his nape) and has totally won her heart.

Initially, my sister just liked him and never thought she would actually fall in love with him but they started meeting frequently and became extremely close.
Now she can't imagine herself without him.

The worst part is this guy's attitude and behaviour. He has been a chain smoker since he was 16. He does weed. Gets drunk and high. he's even had allegations of drug abuse and has been a womanizer. He has this toxic personality and his own friends claim he is quite negative and toxic.

My sister has been dealing with him and all his problems as if she is his babysitter. Many times he gets high and completely intoxicated and she's the one who puts him to sleep and such. He has suffered from health issues and she had dedicated all her time to him. She has been persuading him to give up smoking and substances.

She told me she can do anything to make him happy and no longer has any friends because she spends all her time with him. My sister even went to the extent of being physical with him every single day of a certain week , only to keep him pleased.

Also, he is quite a possessive guy and she does as he does. If he gets jealous or something, she ll stop talking to the guy and devote all her time with him.

I am concerned about my sister's well being and I don;t know where she's heading. Help!