Hmmm, so her family could be the root of her problems? So it could be that she’s using substances to “block out” unwanted emotions and feelings as a quick fix rather than coping / dealing with them?
The fact she tells you at all would suggest she does trust you, and love you. It’s very hard for an addict to admit to anyone, let alone themselves, so its a credit to her, and you that she can talk to you, thats a good start.
Does she show an interest in stopping, like in a serious emotional way? I’m guessing you will have already had the “I can take it or leave it” and “yeah I’m going to stop” but has she admitted she has a problem, or said she “wants” to stop?