Emily - first, welcome to the forum - this is a great place to get some advice, strength and support for yourself. And congratulations on your 2 years being clean!
I am afraid that I don't have any great pearls of wisdom to offer you - but someone else will undoubtedly be along soon, maybe they will do better.
For your friend - do you know why her mother took over the care of her daughter? From what you wrote, this seems to have been a key event / trigger for your friend. She obviously has serious self-worth issues if she thinks her daughter would be better off without her and contemplates suicide on a somewhat regular basis.
Perhaps you could do a little research and see if you can find a NA meeting in your area - offer her recovery resources and support. Take her to a meeting maybe something will click for her. Her first step will be admitting that she has a problem - NA has some literature to help folks come to that realization and quit denying it.
You need to accept that your friend will not get clean until she wants to - nothing you can do will make her get and stay sober until she wants it for herself. Just like you did, once she makes her decision, she will be hard to stop!
Just today, I got this from a friend who has two sons that are heroin addicts, know that he is NOT alone in his vigil - "...as always I'll pray for all and I mean ALL who suffer."
In the words of another member here: "Love cannot save our addicted loved ones, if it could, not one of us would be here." - Ann from SR
Keep coming back,
Jim