I'm sorry to hear that your daughter is still dealing with radiation damage from cancer treatments, resulting in drastic heart failure. Cancer treatment-induced heart disease does happen. There is a discussion on Mayo Clinic Connect dedicated to it here:
– Cancer Treatment Induced Heart Disease https://connect.mayoclinic.org/discussion/radiation-induced-heart-disease/
Has your daughter been seen at a Cardio-Oncology clinic? Have you and your daughter considered a second opinion regarding her qualification for a heart transplant? May I ask what type of cancer your daughter had?