Unfortunately what you are experiencing is very typical addict behavior. They try to make their loved ones feel guilty for disconnecting from the their irrational and often dangerous behaviors. When we disengage......detach with love, it doesn't mean that we don't love them but I'm sure it looks that way from their perspective.
At some point in time, self preservation comes into play. We have to do what is best for us. The reason that her words sting is because there is an element of truth to them. You and your parents HAVE pulled back....but you've also made it extremely clear that she will have support if/when she decides to seek recovery. And at that point (when she makes that decision) I do believe that family support and encouragement becomes very important.
Just because your sister says something doesn't make it true. The "my family has abandoned me" is a method of gaining sympathy from others (including the family members who desperately want to prove to the addict that they are loved).
Do what you need to do for you and your family. Setting boundaries is important. You can say what you mean (state the boundary clearly), mean what you say (your boundary is not negotiable) and not say it mean.
gentle hugs
ke