Hi Kate it's the right thing to do, but it's so hard. My heart goes out to you. I hope that now you're stopping all help except food that she finally realises she has to do this for herself.
Heartless as it seems, you removing that safety net in her mind might be the mental snap she needs to have. It's like she's been counting on someone coming through with money, rehab, whatever so she can keep using just that bit longer.