It involves a transplant (and that means there aren't as many to go around), which means that they do have to believe the resources exist to ensure the transplants success (unfortunately that includes ongoing cost of immunosuppressive medication).
So she is being rejected IN FAVOR of someone who has the resources to ensure a successful transplant, to not waste one of the few available hearts one an attempt that appears doomed to fail anyways. This is actually one of the key issues of the healthcare debate: how to distribute resources that are limited. While "whoever has the most money" seems an unfair way to determine who gets the limitted number of heart transplants, it's no more "unfair" than a random lottery system