My friend is in alot of trouble. help!?

Okay my friend is 17, her names Jessica. Now i will admitt i was so jelous of that girl, she was a ********* stunner, whenever i was with her she would stop to talk to guys she knew. I always thought she was perfect... Unfortunately 2 years ago her mum died because of drink related problems and her dad was left to cope with her older brother(rowan), her other brother(josh) and a baby sister(kayla). her oldest brother moved out with his child and her other brother went with him. as you can imagine a 19 year old isnt the most resposible so josh ended up in lots of trouble with the police and fighting. anyway the thing about Jess was she would never admitt she was hurting or upset she would bottle it up and to get rid of the pain she would drink. it was 2 years ago and she drank every week excessively for a year untill her dad found a girl friend. Now trust Jess doesnt like alot of people and when it comes to her familly she doesnt like anyone interfearing, however Jess liked this woman and when i met her they were exactly the same both ust as beautiful and secretive. anyway jess learnt to adore her even if she didnt admitt it. she stopped drinking, hanging out with the wrong people, started going to school again. unfortunately she died 2 months ago of a drug overdose, i knew jess would be crushed but she was always a strong person so i figured she'd be ok. shes not, shes drinking more than usuall hasnt been to college for 2 months, shes with a different guy every day. and tbh im just worried. i dont know how to help her?