I have no advice to help them, but I'd warn you, as a care giver, to be sure not to let their problems spiral your own life. I've seen several former addicts lapse after trying to rescue their friends - if you're not in a stable place it's important not to let someone destabilize you and just suggest supports that might be able to handle your friend.
Other folks might have more useful advice, but it's important to realize that mental health is a constant struggle and life isn't forever - if your friend has lost a limb they have a very narrow road to walk to recovery and, without proper supports, it's unfortunately a road most people fall off.