Why should the resources of society be used on her yet again?
Well, because she's ill.
That's generally why we treat people, and we don't generally ask how
they became ill, or make treatment decisions based on whether we consider that they fell ill in a morally acceptable way.
The reason that she has been denied a second donor liver transplant is because the supply of donor livers is limited, and they are assigned to those for whom they offer the best chance of success. Her history of relapsing drug abuse is the reason she has denied a transplant, but that is a clinical, not a moral, judgment. If she had metastatic cancer in any organ she would also be denied a transplant, or a pulmonary condition, even though they normally raise no moral issues.
The issues are slightly different when it comes to tissue transplantation for a live donor. If this patient has such a transplant, it will not be at the expense of a transplant for someone else, since the donor who is willing to donate 70% of his kidney to this patient is unlikely to be willing to donate it to anyone else. Thus denying her a transplant does not enable us to give a transplant to someone else.
Assuming she is assessed as suitable, all the indications are favourable, etc, then the only reason to deny her a transplant would be to save the cost, not to give a liver to someone else. But I think we go down a very slippery slope if we deny somebody medical treatment because we disapprove morally of the circumstances in which they fell ill. This isn’t an enquiry we normally make in relation to medical treatment; why should we make it on this occasion?